That's the theory of a team of researchers who looked at hundreds of extrasolar planets, or exoplanets, observed by NASA's Transiting Exoplanet Survey Satellite (TESS).

TESS hunts exoplanets by catching them as they cross the face of, or "transit," their parent star, which causes a tiny drop in light from that star. The study team discovered that light from stars neighboring the one being transited could "contaminate" TESS' data, making it look like the transiting planet is blocking less light than it actually is. And that would make the planet look smaller than it is.

"We found that hundreds of exoplanets are larger than they appear, and that shifts our understanding of exoplanets on a large scale," University of California, Irvine researcher and team leader Te Han said in a statement. "This means we may have actually found fewer Earth-like planets so far than we thought."

Exoplanets throw shade

Exoplanets are so distant and faint that it is only on rare occasions that astronomers can image them directly.

That means the transit method has become the most successful way of detecting worlds beyond the solar system. It requires the planet and its star to be at the right angle in relation to Earth, and for astronomers to wait for the planet to make two transits to confirm its existence.

The transit method is best at spotting short-period planets orbiting close to their host stars, because they make more frequent transits. The method also favors larger planets, which block more light.

"We’re basically measuring the shadow of the planet," said team member and UC Irvine astronomer Paul Robertson.

The team gathered hundreds of TESS observations of exoplanets, sorting them by the width of the exoplanets in question.

They then used computer modeling and data from the European Space Agency's (ESA) star-tracking mission Gaia to estimate how much light contamination TESS is experiencing during its observations.

"TESS data are contaminated, which Te's custom model corrects better than anyone else in the field," said Robertson. "What we find in this study is that these planets may systematically be larger than we initially thought. It raises the question: Just how common are Earth-sized planets?"

Move over Earth-like worlds: ocean planets could be more common

Because of the biases of the transit method mentioned above, the number of exoplanets detected with TESS having sizes and compositions similar to those of Earth was already low.

"Of the single-planet systems discovered by TESS so far, only three were thought to be similar to Earth in their composition," Han explained. "With this new finding, all of them are actually bigger than we thought."

The likely outcome of this is that those exoplanets are larger ocean planets or "hycean worlds" covered by a large single ocean. Those worlds could also be gas giants smaller than Jupiter, like Neptune and Uranus.

That impacts the search for life because, though hycean worlds are packed with water, they could be lacking other ingredients needed for life to arise.

"This has important implications for our understanding of exoplanets, including, among other things, prioritization for follow-up observations with the James Webb Space Telescope, and the controversial existence of a galactic population of water worlds," Roberston added.

The next step for Han, Roberston, and colleagues is to re-examine planets previously deemed uninhabitable due to their size, to see if they are larger than previously thought.

In the meantime, the research is a reminder to astronomers to be cautious when assessing TESS data.

The team's research was published on Monday (July 14) in the Astrophysical Journal Letters.

These lakes and Titan's seas are filled with liquid hydrocarbons like ethane and methane rather than water. And though we know water is a key ingredient of life on Earth, astrobiologists have theorized that Titan's liquid hydrocarbons could allow the molecules needed for life to form, whether that life is similar to what we see on Earth or a very different form of life.

This new research suggests a way vesicles could form on Titan based on what we know about its atmosphere and chemistry. The formation of such compartments is a key step on the road to the development of "protocells."

"The existence of any vesicles on Titan would demonstrate an increase in order and complexity, which are conditions necessary for the origin of life," Conor Nixon of NASA's Goddard Space Flight Center said in a statement.

"We're excited about these new ideas because they can open up new directions in Titan research and may change how we search for life on Titan in the future."

The path to life starts with pockets

The process of creating vesicles begins with molecules called amphiphiles, dual-nature molecules with both water-loving (hydrophilic) and water-repellent (hydrophobic) ends. Under certain conditions, these molecules can self-organize to create vesicles.

On Earth, when amphiphiles meet water, they group together to form spheres similar to soap bubbles with the water-loving end facing outwards, protecting the hydrophobic end.

If two layers of amphiphiles are together, they can form a bilayer "ball" with a shell of water sandwiched between the two layers of molecules. A structure that resembles a living cell.

This process would be very different on Titan due to its environment, one that is radically different than Earth's.

Titan isn't just the largest moon in the solar system; it is also the moon with the densest atmosphere. This is primarily because of Titan's cool temperature and its distance from the sun, which prevents its atmosphere from being stripped by the solar wind.

From 2004 to 2017, the Cassini spacecraft was able to stare through this substantial atmosphere to discover how the meteorological cycle of Titan has influenced its surface.

Though the majority of Titan's atmosphere is composed of nitrogen, its clouds are composed of methane that erodes the surface and river channels as it falls as rain and fills its lakes and seas. When exposed to sunlight, the methane evaporates and rises to the atmosphere again, regenerating Titan's clouds.

The activity of methane through Titan's atmosphere allows complex chemistry to happen, particularly when sunlight splits methane molecules, creating fragments that recombine as complex organic molecules.

This team theorizes that vesicles might form on Titan when sea-spray droplets are thrown into the atmosphere by methane raindrops landing on the surface of lakes and seas.

If the surfaces of Titan's seas are coated with layers of amphiphiles, the sea-spray droplets will be too. That means when those launched droplets fall back to the methane seas, they meet the amphiphile sea-layer and form a bilayer vesicle, enclosing the original droplet.

Over time, these vesicles could be dispersed through the lakes and seas, interacting and potentially leading to the creation of protocells.

The discovery is sure to generate excitement for NASA's forthcoming Dragonfly mission, which will set off for Titan in 2028. Arriving in 2034, the nuclear-powered rotocopter craft aims to explore prebiotic chemistry and habitability on the Saturnian moon.

Understanding this process as it occurs on Titan, if it is occurring, could shed light on the mystery of how life emerged on Earth.

The team's research was published on July 10 in the journal International Journal of Astrobiology.

"It's harder, but certainly not impossible, to live in these conditions," Christopher Glein, an ocean worlds scientist at the Southwest Research Institute (SwRI) in San Antonio told Space.com.

Cassini discovered Enceladus' plumes of water vapor, which jet out from large cracks in the icy surface called "tiger stripes" at the moon's southern polar region, in 2005. Although the Cassini mission, which ended in a blaze of glory in September 2017 when the orbiter plunged into Saturn, was not designed to sample material from such plumes, two of its instruments, the Cosmic Dust Analyzer and the Ion and Neutral Mass Spectrometer, were able to at least get a taste of them during close flybys of the icy moon. What they found offered clues as to the contents of the ocean deep within Enceladus that feeds the plumes.

"The payoff from Cassini far exceeded what it was designed to accomplish," said Glein. "We discovered a habitable ocean at Enceladus."

Those measurements remain our best study so far of any of the ocean moons of the outer solar system, and through geochemical modeling scientists are able to draw some conclusions. New research — by Glein and his SwRI colleague, planetary archaeologist Ngoc Truong — has determined that the pH of the ocean beneath Enceladus' ice is moderately high, between 10.1 and 11.6

The pH scale is a measure of how acidic or alkaline something is, 1 being highly acidic, 14 being highly alkaline, and 7 being neutral. Hence Enceladus' ocean is quite alkaline. For comparison, Earth's ocean has a pH of about 8.

The researchers arrived at this conclusion by studying the abundance and distribution of phosphate minerals in the ice grains within the plumes, in particular the ratio of mono-hydrogen phosphate (HPO4) to regular phosphate (PO4), which is a direct indicator of the pH level of the water. The range of possible pH that Glein and Truong found is higher than the previous estimates of 8 to 9. However, those estimates were made before 2023, when further detailed analysis of Cassini's data revealed high concentrations of phosphates in the plumes.

The alkalinity is a signature of interactions between water and iron-, magnesium- and sodium-bearing silicate rock on the ocean floor. These water-rock interactions release sodium hydroxide (NaOH) into the ocean that subsequently reacts with carbon dioxide and produces the high alkalinity.

"One consequence of these conditions is a high carbonate alkalinity, which supercharges the solubility of calcium phosphate minerals — like apatite. Your teeth might dissolve in Enceladus' ocean," said Glein.

Such high alkalinity would be somewhat challenging for life. "High pH tends to break apart biological polymers," said Glein when asked by Space.com. "However, we know that some microbes on Earth can tolerate the range of pH found on Enceladus."

These terrestrial, alkaline-loving microbes are extremophiles called alkaliphiles. And there's another boost for the possibility of life in Enceladus' ocean, since the water-rock interactions produce minerals and ions that can be used by microbial life for energy and sustenance. The conditions even provide clues as to where in the ocean we might find such life, should it exist there.

"Metals become less soluble at higher pH, so iron may be scarce in Enceladus' ocean," said Glein. "I think the best place to live would be at the seafloor. If you're a microbe, you could directly 'mine' iron and other metals from minerals without relying on solubility. We might want to think about biofilms on Enceladus."

Based on the alkalinity, the chemical composition of the plumes as measured by Cassini and the expected minimal outgassing of carbon dioxide from the ocean, Glein and Truong have assembled a list of minerals and molecules that we could expect to find in Enceladus' ocean. The most abundant compounds on the list are sodium, chlorine, sodium carbonate, carbonate ions, ammonia and potassium ions.

"The composition does make sense for deep circulation of ocean water through the rocky core of Enceladus," said Glein.

One surprise was the inferred high abundance of molecular hydrogen (H2). However, its concentration is similar to some deep-sea environments on Earth, such as the vast field of hydrothermal vents in iron-rich rocks called the "Lost City" deep in the Atlantic Ocean.

"There, H2 supports life by supplying a source of chemical energy," said Glein.

Although the list of mineral constituents in the ocean is not confirmed — we'd have to return to Enceladus to do that — it just shows that we don't need to venture into the depths of the dark water to learn the ocean's secrets. Just flying through the plumes is enough to give us a good indication. Cassini did so without specialized equipment for analyzing molecules and compounds within the plumes, since when it was launched (October 1997) the plumes had not even been discovered. Glein thirsts to return with a dedicated mission carrying state-of-the-art instruments specifically designed for the job.

"Imagine what we could find," he mused. "The picture for Enceladus is of an ocean that is intensely affected by water-rock interactions. Enceladus is a geochemical paradise!"

Glein and Truong's findings were published online June 20 in the journal Icarus.

Grandiose headlines often promise proof that we are not alone, but scientists remain cautious. Is this caution unique to the field of astrobiology? In truth, major scientific breakthroughs are rarely accepted quickly.

Newton’s laws of motion and gravity, Wegener’s theory of plate tectonics, and human-made climate change all faced prolonged scrutiny before achieving consensus.

But does the nature of the search for extraterrestrial life mean that extraordinary claims require even more extraordinary evidence? We’ve seen groundbreaking evidence in this search beforehand, from claims of biosignatures (potential signs of life) in Venus’s atmosphere to NASA rovers finding “leopard spots” – a potential sign of past microbial activity – in a Martian rock.

Both stories generated a public buzz around the idea that we might be one step closer to finding alien life. But on further inspection, abiotic (non-biological) processes or false detection became more likely explanations.

In the case of the exoplanet, K2-18 b, scientists working with data from the James Webb Space Telescope (JWST) announced the detection of gases in the planet’s atmosphere – methane, carbon dioxide, and more importantly, two compounds called dimethyl sulphide (DMS) and dimethyl disulphide (DMDS). As far as we know, on Earth, DMS/DMDS are produced exclusively by living organisms.

Their presence, if accurately confirmed in abundance, would suggest microbial life. The researchers even suggest there’s a 99.4% probability that the detection of these compounds wasn’t a fluke – a figure that, with repeat observations, could reach the gold standard for statistical certainty in the sciences. This is a figure known as five sigma, which equates to about a one in a million chance that the findings are a fluke.

So why hasn’t the scientific community declared this the discovery of alien life? The answer lies in the difference between detection and attribution, and in the nature of evidence itself.

JWST doesn’t directly “see” molecules. Instead, it measures the way that light passes through or bounces off a planet’s atmosphere. Different molecules absorb light in different ways, and by analysing these absorption patterns – called spectra – scientists infer what chemicals are likely to be present. This is an impressive and sophisticated method – but also an imperfect one.

It relies on complex models that assume we understand the biological reactions and atmospheric conditions of a planet 120 light years away. The spectra suggesting the existence of DMS/DMDS may be detected because you cannot explain the spectrum without the molecule you’ve predicted, but it could also result from an undiscovered or misunderstood molecule instead.

Climate comparison

Given how momentous the conclusive discovery of extraterrestrial life would be, these assumptions mean that many scientists err on the side of caution. But is this the same for other kinds of science? Let’s compare with another scientific breakthrough: the detection and attribution of human-made climate change.

The relationship between temperature and increases in CO₂ was first observed by the Swedish scientist Svante Arrhenius in 1927. It was only taken seriously once we began to routinely measure temperature increases. But our atmosphere has many processes that feed CO₂ in and out, many of which are natural.

So the relationship between atmospheric CO₂ and temperature may have been validated, but the attribution still needed to follow.

Carbon has three so-called flavors, known as isotopes. One of these isotopes, carbon-14, is radioactive and decays slowly. When scientists observed an increase in atmospheric carbon dioxide but a low volume of carbon-14, they could deduce that the carbon was very old – too old to have any carbon-14. Fossil fuels – coal, oil and natural gas – are composed of ancient carbon and thus are devoid of carbon-14.

So the attribution of anthropogenic climate change was proven beyond reasonable doubt, with 97% acceptance among scientists. In the search for extraterrestrial life, much like climate change, there is a detection and attribution phase, which requires the robust testing of hypotheses and also rigorous scrutiny.

In the case of climate change, we had in situ observations from many sources. This means roughly that we could observe these sources close up. The search for extraterrestrial life relies on repeated observations from the same sensors that are far away. In such situations, systematic errors are more costly.

Further to this, both the chemistry of atmospheric climate change and fossil fuel emissions were validated with atmospheric tests under lab conditions from 1927 onwards. Much of the data we see touted as evidence for extraterrestrial life comes from light years away, via one instrument, and without any in situ samples.

The search for extraterrestrial life is not held to a higher standard of scientific rigor but it is constrained by an inability to independently detect and attribute multiple lines of evidence.

For now, the claims about K2-18 b remain compelling but inconclusive.

That doesn’t mean we aren’t making progress. Each new observation adds to a growing body of knowledge about the universe and our place in it. The search continues – not because we’re too cautious, but because we are rightly so.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

That's according to scientists who have found that lichen in the Mojave Desert managed to survive for 3 months under levels of intense radiation from the sun that had previously been considered lethal to this organism.

While the lichen was badly damaged, it was able to recover and eventually replicate. That indicates to scientists that other extraterrestrial life that requires photosynthesis could prosper on terrestrial or rocky extrasolar planets, or "exoplanets," even if they are exposed to radiation from their own star that had previously been considered deadly.

"The study was motivated by a curious observation," team member and Desert Research Institute scientist Henry Sun said in a statement. "I was just walking in the desert, and I noticed that the lichens growing there aren't green, they're black. They are photosynthetic and contain chlorophyll, so you would think they'd be green.

"So I wondered, 'What is the pigment they're wearing?' And that pigment turned out to be the world's best sunscreen."

Lichen is composed of algae or cyanobacteria that exist symbiotically with fungi. The lichen that formed the basis of this research is Clavascidium lacinulatum, or the "common lichen," found in arid regions across the globe, including Europe, Asia, North Africa, and, of course, the U.S.

Common lichen. Not so common sunscreen

Life on Earth thrives on light from the sun, which plants and other life forms use to create sugars via photosynthesis. But sunlight is a mix of electromagnetic radiation of different wavelengths, and some of this radiation is not so useful to life; in particular, ultraviolet light.

Terrestrial organisms have evolved to cope with Ultraviolet A (UVA) radiation and less common UVB radiation. In humans, UVA is associated with skin aging and wrinkle formation, while UVB causes skin damage like tanning, sunburn, and can even lead to skin cancer.

However, light that leaves our star also contains UVC radiation, which has a shorter wavelength than UVA or UVB light and carries more energy, making it much more harmful to life, damaging DNA, and preventing reproduction. In fact, UVC is so lethal that it can be used to sterilize air and water, wiping out microorganisms like bacteria and viruses.

Fortunately, our atmosphere filters out much of the ultraviolet light blasted at us from the sun, protecting life from its harshest effects. UVC radiation is completely absorbed, meaning it doesn't reach the surface of our planet. But terrestrial worlds in other star systems may not be so lucky.

This could be especially detrimental to life around so-called M-class and F-class stars, which are hotter and brighter than the sun and are known to belt out intense UVC radiation, especially during stellar flares.

"After the launch of the James Webb Space Telescope (JWST), which can see extremely far into space, the excitement shifted from finding life on Mars to these exoplanets," Sun said. "We're talking about planets that have liquid water and an atmosphere."

Sun and colleagues wanted to see how lichen coped with bombardment by UVC radiation, so they placed a sample next to a UVC lamp for 3 months in a controlled setting.

"In order for a microorganism to persist on a planet, it has to last longer than a day," Sun explained. "So, our experiment had to be long enough to be ecologically significant. We also wanted to go beyond just activity and demonstrate viability."

To their surprise, half the cells comprising the lichen regained the ability to replicate after water was reintroduced to them.

After further investigation with chemists from the University of Nevada, Sun and colleagues found that this is because the acids of the lichen are akin to nature's version of the additives used to make plastics UV-resistant.

Diving deeper, the team cut through the lichen, finding that the top layer was darker, almost like a suntan in humans. Furthermore, they found that when the fungi and the algae that make up lichen were separated, the algae died within minutes of UVC exposure.

The team surmised that because lichen isn't regularly exposed to UVC thanks to Earth's atmosphere, its protective layer evolved as a bonus of its UVA and UVB shielding rather than as an aid to survival.

"We came to the conclusion that the lichen's top layer—a less than millimeter thick skin, if you will—assures that all the cells below are protected from radiation," Sun continued. "This layer acts as a photostabilizer and even protects the cells from harmful chemical reactions caused by the radiation, including reactive oxygen."

As for this discovery's implications for life on other worlds, the team posits that some exoplanets may "be teeming with colonial microorganisms that, like the lichens in the Mojave Desert, are 'tanned' and virtually immune to UVC stress."

"This work reveals the extraordinary tenacity of life even under the harshest conditions, a reminder that life, once sparked, strives to endure," team leader and NASA Goddard Space Flight Center researcher Tejinder Singh said. "In exploring these limits, we inch closer to understanding where life might be possible beyond this planet we call home."

The team's research was published on June 12 in Astrobiology

The signs were rooted in a tentative detection of dimethyl sulfide (DMS) — a molecule produced on Earth solely by marine life — and/or its close chemical relative DMDS, which is also a potential biosignature, in the atmosphere of the exoplanet. This finding, along with the possibility that K2-18b is a "Hycean world" with a liquid water ocean, sparked significant interest about its potential to support life.

However, these results have sparked intense debate among astronomers. While recognizing this finding would be a groundbreaking achievement and a major testament to the James Webb Space Telescope's (JWST) capabilities if true, many scientists remain skeptical, questioning both the reliability of the detected DMS signature as well as whether DMS itself is a dependable sign of life in the first place. As such, many independent teams have been conducting follow-up studies about the original claims — and a newly published one only adds to the debate, suggesting the Cambridge scientists' DMS detection wasn't significant enough to warrant the publicity it received.

"Among the physical sciences, astronomy enjoys a privileged position," Rafael Luque, a post doctoral researcher at the University of Chicago, told Space.com. "It is more frequently covered in the media thanks to its visual appeal and the big philosophical and universal questions it addresses. It was therefore expected that — even if tentative — the detection of a potential biomarker in the atmosphere of an exoplanet would have extensive coverage."

The significance of significance

Luque and his colleagues, including fellow postdoctoral researchers Caroline Piaulet-Ghorayeb and Michael Zhang, remain unconvinced that what astronomers observed on K2-18b was in fact a credible signature indicating life. In a recent arxiv preprint — which is yet to be peer-reviewed — their team re-examined the validity of the original evidence. "This is how science works: evidence and counterevidence go hand in hand,” he stated.

When scientists study data from different instruments separately, they might end up with conflicting results — it's like finding two different "stories" about a subject that don't match. "This is, in fact, what happened in the original team's papers," Zhang told Space.com. "They inferred a much higher temperature from their MIRI (mid-infrared) data than from their NIRISS and NIRSpec (near-infrared) data. Fitting all the data with the same model ensures that we're not telling contradictory stories about the same planet."

Thus, the team conducted a joint analysis of K2-18b using data from all three of the JWST's key instruments — the Near Infrared Imager and Slitless Spectrograph (NIRISS) and the Near Infrared Spectrograph (NIRSpec), which capture near-infrared light, and the Mid-Infrared Instrument (MIRI), which detects longer mid-infrared wavelengths. The goal was to ensure a consistent, planet-wide interpretation of K2-18b's spectrum that the team felt the original studies both lacked.

"We reanalyzed the same JWST data used in the study published earlier this year, but in combination with other JWST observations of the same planet published […] two years ago," Piaulet-Ghorayeb told Space.com. "We found that the stronger signal claimed in the 2025 observations is much weaker when all the data are combined."

These signals may appear weaker when all data is combined because the initial "strong" detection may have been overestimated, the team says, due to being based on a limited initial data set. Combining data from multiple sources lets scientists cross-check and verify the strength — and validity — of a particular signal.

"Different data reduction methods and retrieval codes always give slightly different results, so it is important to try multiple methods to see how robust the results are," explained Piaulet-Ghorayeb. "We never saw more than insignificant hints of either DMS or DMDS, and even these hints were not present in all data reductions."

"Importantly, we showed that when testing a wider range of molecules that we expect to be produced abiotically in the atmosphere, the same observed spectral features can be reproduced without the need for DMS or DMDS," she continued.

More than one path to a result

Molecules in an exoplanet's atmosphere are typically detected through spectral analysis, which identifies unique "chemical fingerprints" based on how the planet's atmosphere absorbs specific wavelengths of starlight as it passes — or transits — in front of its host star. This absorption leaves distinct patterns in the light spectrum that reveal the presence of different molecules.

"Each molecule’s signature is unique, but different molecules can have some features that fall in similar places because of their close molecular structures," explained Piaulet-Ghorayeb.

The difference between DMS and ethane — a common molecule in exoplanet atmospheres — is just one sulfur atom, and current spectrometers, including those on the JWST, have impressive sensitivity, but still face limits. The distance to exoplanets, the faintness of signals, and the complexity of atmospheres mean distinguishing between molecules that differ by just one atom is extremely challenging.

"It is widely recognized as a huge problem for biomarker detection, though not an insurmountable one, because different molecules do have subtly different absorption features," said Piaulet-Ghorayeb. "Until we can separate these signals more clearly, we have to be especially careful not to misinterpret them as signs of life."

Beyond technical limitations, another source of skepticism is how the data has been interpreted statistically. Luque points out that the 2023 study described the detection of DMS as "tentative," reflecting the preliminary nature of the finding. However, the most recent 2025 paper reported that the detection of DMS and/or DMDS reached 3-sigma significance — a level that, while below the 5-sigma threshold required for a confirmed discovery, is generally considered moderate statistical evidence.

"Surprisingly, this latest work was used to double down on the claim for DMS and even more complex molecules to be present. The detection, however, is not statistically significant nor robust, as we show in our work.

Despite these uncertainties, the team is worried that media coverage has continued to spotlight bold claims about DMS and other molecules. "The [JWST] telescope is incredibly powerful, but the signals we're detecting are very small. As a community, we have to make sure that any claims we make about a planet’s composition are robust to the choices made when processing the data from the telescope," said Piaulet-Ghorayeb.

"Researchers have the responsibility to double-check and verify, but the media is also responsible for duly reporting these follow-up works to the general public," added Luque. "Even if they have less catchy titles."

"As Carl Sagan once said, 'extraordinary claims require extraordinary evidence,'" said Luque. "That threshold was not met by how the results were disseminated to the general public."

Whether we'll ever get a clear answer about life on K2-18 b is uncertain — not just because of technological limits, but because the case for follow-ups with the JWST may simply not be strong enough. "JWST is continuing to observe K2-18b, and even though the new observations won't have the ability to detect life, we will soon find out more about the planet's atmosphere and interior," Zhang said.

Recently, the Coller Dolittle Challenge awarded the winner of its first $100,000 annual prize to accelerate progress toward interspecies two-way communication. A prize of equal value will be awarded every year until a team deciphers the secret to interspecies communication.

This year's winning team of researchers has discovered that dolphin whistles could function like words — with mutually understood, context-specific meaning.

Crack the code

The winning team was led by Laela Sayigh from the Woods Hole Oceanographic Institution. The researchers are studying the resident bottlenose dolphin community offshore of Sarasota, Florida.

They were on the lookout for "non-signature" whistles, which comprise approximately 50% of the whistles produced by Sarasota dolphins. Non-signature whistles differ from the more widely studied "signature" whistles, which are referential, name-like vocalizations.

Sayigh's team used non-invasive suction-cup hydrophones, which they placed on the dolphins during unique catch-and-release health assessments, as well as digital acoustic tags.

"Bottlenose dolphins have long fascinated animal communication researchers," Sayigh said in a statement. "Our work shows that these whistles could potentially function like words, shared by multiple dolphins."

Sayigh and her team can now use deep learning in an attempt to "crack the code" and analyze those whistles.

Zoologist's guide to the galaxy

But what does all this have to do with E.T.?

"My interests are very firmly here on Earth, in learning about how dolphins communicate with each other," Sayigh told Space.com "I do know that there are others in the animal communication world that are interested in this, however."

One of those researchers is Arik Kershenbaum, an associate professor and director of studies at Girton College, part of the University of Cambridge in England. He's the author of "The Zoologist's Guide to the Galaxy: What Animals on Earth Reveal About Aliens — and Ourselves" (Viking, 2020).

Kershenbaum explained that the book is about life on Earth, because "that's all we have to look at." He also contributed a white paper for a workshop at the Search for Extraterrestrial Intelligence (SETI) Institute in California, titled "What Animal Studies Can Tell Us about Detecting Intelligent Messages from Outside Earth."

Cross-species database

In that paper for the SETI Institute, Kershenbaum and colleagues concluded that animal communication research is the closest we are likely to get to studying extraterrestrial signals, until such signals are actually received.

"Many of the challenges facing SETI research are similar to those already addressed in the investigation of animal behavior, and the evolutionary origins of human language," they wrote. "Indeed, the evolution of language on Earth may in fact have been driven and constrained by similar principles to those operating on life on other planets."

The researchers have proposed the establishment of a large cross-species database of communicative signals, made available to all SETI and animal behavior researchers.

In addition, they also proposed that tools, algorithms and software used to analyze these signals should be made publicly available for application to these data sets, "so that comparative studies can take full advantage of the expertise from the biological, mathematical, linguistic and astronomical communities."

Complex vocalizations

The topic of dolphin language interpretation, as well as the vocalizations of humpback whales and the field of non-human communications more broadly, is increasingly drawing the interest of SETI researchers and astrobiologists, explained Bill Diamond, president of the SETI Institute.

Humpback whales have very complex vocalizations, Diamond told Space.com, "where it seems clear that they are transmitting information and not simply making sounds associated with mating, feeding or dealing with threats. They plan ahead and communicate complex instructions to one another."

Leading that look is SETI researcher Laurance Doyle, who's working on a project in partnership with the Alaska Whale Foundation to study the vocalizations of humpback whales.

Fundamental rules

For Diamond, the relevant research question is whether or not there are some fundamental mathematical rules associated with the transmission of information that would be universal — like the laws of physics and chemistry — within our known universe.

"If there's an underlying rule structure to the transmission of information, and we can decipher it," Diamond said, "we would firstly be able to recognize a detected SETI signal as containing information, and therefore intelligence. And, possibly, we might even ultimately be able to translate it!"

According to Diamond, "there's definitely a connection between SETI/astrobiology and the study of non-human communication and non-human intelligence."

Scientists from NASA's Jet Propulsion Laboratory (JPL) in Southern California, along with researchers in India and Saudi Arabia, have discovered 26 previously unknown bacterial species in the clean rooms that were used to prep NASA's Phoenix Mars lander for its August 2007 launch.

Clean rooms are decontaminated and intensely controlled environments specifically designed to prevent microbial life from hitching a ride into space. But some microorganisms, known as extremophiles, show impressive resilience in inhospitable environments, whether that's the vacuum of space, hydrothermal vents on the slopes of undersea volcanoes, or even NASA clean rooms.

"Our study aimed to understand the risk of extremophiles being transferred in space missions and to identify which microorganisms might survive the harsh conditions of space," study team member Alexandre Rosado, a researcher at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, said in a statement.

"This effort is pivotal for monitoring the risk of microbial contamination and safeguarding against unintentional colonization of exploring planets," Rosado added.

These hardy microbes may also offer insights that could benefit life on Earth. The scientists performed genetic research on samples gathered from the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center in Florida, one of the last stops for Phoenix before its launch from neighboring Cape Canaveral Space Force Station (then known as Cape Canaveral Air Force Station).

They found 53 strains that they determined belonged to 26 novel species. And they dug into the genomes of these newfound extremophiles, looking for clues that could help explain their extraordinary survivability. The keys might be in genes linked to DNA repair, detoxification of harmful substances and boosted metabolism, according to the team.

"The genes identified in these newly discovered bacterial species could be engineered for applications in medicine, food preservation and other industries," said Junia Schultz, a postdoctoral fellow at KAUST.

And, of course, the research will help NASA improve its clean room protocols to minimize the risk of biological contamination on future missions.

"Together, we are unraveling the mysteries of microbes that withstand the extreme conditions of space — organisms with the potential to revolutionize the life sciences, bioengineering and interplanetary exploration," said Kasthuri Venkateswaran, a retired JPL scientist and a lead author of the study on the research, which was published May 12 in the journal Microbiome.

The image, a blurry composite of more than a thousand grayscale snapshots later colorized by scientists, was taken during a precision flyby of Mars on March 1, 2025. At its closest point, the spacecraft skimmed just 550 miles (884 kilometers) above the Martian surface, in a maneuver known as a gravity assist, which used the Red Planet's gravitational pull to slow the spacecraft and adjust its orbit around the sun ahead of a crucial leg of its nearly 2-billion-mile (3.2 billion km) journey to Jupiter.

The brief encounter also served a scientific purpose: It gave the mission team a chance to test the spacecraft's instruments in deep space, including the thermal imager E-THEMIS (short for Europa Thermal Imaging System), which will eventually scan Europa's surface for signs of recent or ongoing geologic activity. Over an 18-minute span on March 1, the instrument took over 1,000 grayscale images — one per second — which began arriving on Earth on May 5, according to a NASA statement.

To confirm the instrument's accuracy, the mission team compared the new infrared imagery with long-term thermal maps of Mars gathered by NASA's Mars Odyssey orbiter, which has been observing the Red Planet since 2001. The Odyssey team even coordinated observations before, during, and after the Europa Clipper flyby to allow for a direct side-by-side comparison, according to the statement.

"We wanted no surprises in these new images," Phil Christensen, a professor of earth and space exploration at Arizona State University who serves as the principal investigator of the E-THEMIS instrument, said in the statement. "The goal was to capture imagery of a planetary body we know extraordinarily well and make sure the dataset looks exactly the way it should, based on 20 years of instruments documenting Mars."

E-THEMIS detects infrared light — essentially heat — allowing scientists to map temperatures across a planetary surface. After the spacecraft reaches the Jupiter system in 2030, these thermal scans will help identify hotspots that could point to recent geologic activity beneath Europa's icy shell, according to the statement.

Infrared imaging will also help pinpoint where Europa's vast subsurface ocean might lie closest to the surface, scientists say. The moon is etched with ridges and fractures, features that scientists suspect result from oceanic forces — like rising water or convection currents — pulling apart the ice from below.

"We want to measure the temperature of those features," Christensen said. If Europa is active, its fractures could be warmer than surrounding ice — especially where the ocean lies near the surface or past eruptions left lingering heat, he added.

The Mars flyby also marked the first full in-flight test of Clipper's radar instrument, which couldn't be tested in its entirety on Earth due to the size of its antennas. Preliminary telemetry suggests the test was successful, with detailed analysis of the data still to come, the statement read.

With the Mars flyby complete, Clipper's next gravity assist will come from Earth in 2026. The spacecraft is expected to enter Jupiter orbit in April 2030, after which it will begin a series of 49 close encounters with Europa that will allow scientists to investigate the moon's life-hosting potential.

While it's not exactly a social science, it turns out bacteria have their own versions of these social structures, too — and because the earliest fossil evidence for life on our planet was indeed bacterial, studying how bacteria live together may help microbiologists piece together how life began on Earth long ago. One day, it may help us discover life on other planets.

Along these lines, in research published last year, scientists took a closer look at the behavior of a type of bacteria called multicellular magnetotactic bacteria (MMB). What they found was fascinating: MMB has a peculiar way of grouping. Despite each member of this bacterial clan existing as a single-celled organism, none of them can survive that way. Instead, they combine together and act as one giant, multicellular organism that scientists call "consortia."

Another special element of MMB is the "magnetotactic" in its name, which means it orients itself based on Earth's magnetic field. If you compare MMB to a social cell of people, which shifts toward a social ideal, MMB orients itself and knows where to be based on the Earth's magnetic poles.

MMB lands "somewhere in-between a single-celled organism and much more complex life" Roland Hatzenpichler, a microbiologist and associate professor in the Department of Chemistry and Biochemistry at Montana State University, Bozeman and author of the new research, told Space.com. He described the consortia as "anywhere from 30 to 100 cells" living together. The sheer existence of MMB also suggests they may be caught in one of the "bottlenecks" of life formation on Earth, according to Hatzenpichler.

In other words, perhaps MMB is caught in a stage of evolution between a single-celled organism and a more complex, multicellular form of life, like an insect or a fish..

In other words, perhaps MMB was not meant to be a single-celled organism, but just couldn't transition to its multicellular future.

MMB doesn't just want to stay connected — it needs to for survival.

Where is MMB found?

The study researchers got their MMB samples from a tidal pool in Massachusetts, which Hatzenpichler is a known site for purple sulfur bacteria. He described the sediment containing the MMB as brown with purple dots.

"The pond itself is basically just this brownish, gooey sediment," Hatzenpichler said. "Sprinkled in are these purple bacteria."

In terms of all known life on Earth, there's really no other organism that compares to MMB, Hatzenpichler said.

There are different species of MMB, Hatzenpichler said, "but they are all pretty related to each other."

Working together; dying together

Compared to single-celled organisms, which can swim freely using their whip-like tails known as "flagella," MMB have some communicating to do in order to move. Otherwise, there would be a conflict of interest, so to speak.

"If the whole thing moves right, it means that the bacterial cells on one side need to stop spinning, or spin the other direction than the ones on the opposing side," Hatzenpichler said.

He explained that in order to pull this off, there "must be some quick social interaction at the very least to communicate, 'okay, who is swimming forward now and who is not doing that.'"

This type of social cuing between bacteria isn't completely unique, though. Hatzenpichler said a bacterial social cueing phenomenon called "quorum sensing" has been studied for a while, and usually dictates movement or helps bacteria discern how many of their own kind are around them. Disease-causing bacteria, for example, may benefit from sticking together as it makes it harder for the immune system to attack, Hatzenpichler explained.

But what is the purpose of MMB — or of multicellular structures that aren’t exactly multicellular? According to Hatzenpichler, scientists don't exactly know. An obvious con is that if a cell ever wants to live individually again, for whatever reason, they can't.

"It's good to work together, right?" Hatzenpichler said. However: "At some point it might not be beneficial anymore to stick around with your buddies. But if you don't, you die."

But cooperating together may also be advantageous if you're able to split up the work. And, on a much smaller scale, scientists may eventually find that what happens in MMB consortia could mirror the different jobs cells have in the human body.

"Your heart cells do something completely different than your brain cells, which are completely different than the lung and so on," Hatzenpichler said. More studies are needed to see if there is such a "mutually exclusive" relationship with MMB, as has been seen among other organisms that don't have an obligate multicellular lifestyle. (Obligate is the scientific term that means the MMB can’t survive if separated as a single cell.)

"We're not there yet, but I think this is basically where the research is going now," he said.

Life formation and being 'more than the sum of parts'

Perhaps the most beautiful thing about MMB is that it poses philosophical questions as well as scientific ones: Is it multicellular or not, and what does MMB say about life that's more complicated than bacteria?

"You could see this entirety of 50 cells as one organism, so to speak, because individually, they die if they separate — they show unified behavior towards a common goal," Hatzenpichler said.

"I think the same argument can be made for an animal," he said. "Sometimes our cells fight for our overall health, and other times, they don’t."

Another takeaway from the latest research on MMB is what it suggests about life formation in general, and how life can build very complex structures out of something comparatively simple, Hatzenpichler said. In the future, it's possible more research on unique organisms like MMB may even aid discovery of life outside Earth.

"You have this emergent phenomena that comes out of that, where the system is more than the sum of its parts."

The team's research was published on July 11, 2024 in the journal PLOS Biology.

Jake Taylor of the University of Oxford in the U.K., who studies atmospheres of exoplanets, used a basic statistical test to identify telltale signs of gas molecules in the atmosphere of the exoplanet at hand, K2-18b. Taylor did this in such a way that the test didn't assume which gases might be present. Instead of the distinct bumps that typically indicate the presence of detectable gas molecules, Taylor saw the data appearing consistent with a "flat line," according to the new study, which was posted to the preprint archive on April 22 and has yet to be peer reviewed. What this means is the data is likely too noisy — or the signal too weak — to draw definitive conclusions.

"This is evidence of the scientific process at work," Eddie Schwieterman, an assistant professor of astrobiology at the University of California, Riverside, who was not involved with the new research, told Space.com. "That's exactly what we want — multiple, independent groups or individuals to analyze and interpret the same data. This is one, and hopefully more will follow."

Aliens or noise?

In 2023, Nikku Madhusudhan of the University of Cambridge and his colleagues first announced the detection of dimethyl sulfide (DMS) on K2-18b, an exoplanet nearly nine times more massive than Earth located about 120 light-years away in the life-friendly "habitable zone" of its star. This detection was made with an instrument on the James Webb Space Telescope (JWST). Then, on April 17, the same team claimed it used a different JWST instrument and found stronger and clearer evidence for the molecule — and a potentially life-rich ocean world — when compared to the 2023 DMS detection, which was not upheld by independent analyses.

On Earth, DMS is almost exclusively produced by life forms like marine algae, making it a possible "biosignature" in the search for extraterrestrial life. "These are the first hints we are seeing of an alien world that is possibly inhabited," Madhusudhan told reporters in a press briefing. "This is a revolutionary moment."

Although the announcement sparked excitement and made global headlines, scientists not involved with the research quickly cautioned that the results are preliminary and come with several caveats.

Chief among them was the fact that Madhusudhan's team reported the DMS detection with three-sigma significance, indicating a 0.3% chance it could be a fluke — well below the five-sigma standard (0.00003% chance) required for solid scientific discoveries. Critics also raised concerns that the team's data pushes the JWST to its limits, noted the absence of expected molecules like ethane that typically appear alongside DMS, and argued that the researchers may have used a biased model that inflated the significance of the DMS detection.

Taylor's findings, based on a simple model commonly used by astronomers as a "first pass" analysis, add to the skepticism, suggesting the detection's significance was overstated. Yet, Madhusudhan and his team remain undeterred, noting that Taylor's models are too simplistic to capture the complex behavior of atmospheric molecules in the wavelengths their JWST data represent.

"There is nothing in this paper that worries me or seems relevant to the discussion about our result," Madhusudhan said in an email to NPR. "I am only slightly surprised that the bar is so low for a rebuttal!"

To confirm a discovery, results must be supported by independent lines of evidence, show strong statistical significance, and rule out non-biological explanations, astrobiologist Michaela Musilova, who was not involved in either of the new studies, told Space.com. "So far, all data we have been able to review related to K2-18b do not meet these requirements."

Back to square one?

Underlying the debate is the broader question of whether K2-18b is even habitable to begin with.

Recent research suggests the planet may be too close to its star to support liquid water on its surface — placing it outside the habitable zone and contradicting earlier conclusions by Madhusudhan and his team that it could be an ocean world. Moreover, scientists announced they found traces of DMS on a cold, lifeless comet in 2024, raising the possibility that such molecules could form through as-yet unknown chemical processes, Musilova noted.

Musilova, Schwieterman and other experts agree additional independent analyses are necessary to determine whether the signals found by Madhusudhan and his team truly represent DMS or DMDS in K2-18b's atmosphere, or are simply the artifact of noise in the data. The signals might be absent, or they could be present but currently undetectable. Either way, more observations are needed to resolve the uncertainty, said Schwieterman.

"If the ultimate result of this story is that the public is more circumspect about future claims of life detection, that's not a terrible thing," he said.

Darryl Z. Seligman is a National Science Foundation Astronomy and Astrophysics Postdoctoral Fellow/Assistant Professor of Physics and Astronomy at Michigan State University.

Scientists owe it to the general public to convey their results accurately and honestly.

Over the last week, I — along with most of my astronomer and planetary scientist colleagues — received emails, texts, and phone calls from family, friends, and the media. Everyone was asking the same question: "Did we really find evidence of life on a planet outside of our own solar system?" This outpouring of communication was prompted by a recent article published by The New York Times entitled "Astronomers Detect a Possible Signature of Life on a Distant Planet."

The Astrophysical Journal Letters recently published an article entitled "New Constraints on DMS and DMDS in the Atmosphere of K2-18 b from JWST MIRI." The peer-reviewed article reported a detection — albeit at low statistical significance — of the presence of dimethyl sulfide (DMS) and/or dimethyl disulfide (DMDS). DMS and DMDS can be produced both by living organisms (such as phytoplankton) or from run-of-the-mill chemical reactions that are not associated with life at all. However, the authors issued a press release only focused on aliens.

If this news article was a wildfire spreading out of control, then every astronomer was a firefighter, desperately trying to minimize the damage spurred by the press release accompanying the paper. Why? Because the news article was exaggerated.

Related: Did we actually find signs of alien life on K2-18b? 'We should expect some false alarms, and this may be one'

This tale is not new to astronomers. In fact, it has played out over and over again: fossilized microbes were found on Mars (nope), an interstellar interloper was an alien spaceship (nope), and bacterial life exists in the clouds of Venus (to be tested), to name a few of our own wolves.

As a collective, we can't resist anthropomorphizing the natural world. Many cultures thought there was a man in the moon, until we learned that his face was a series of craters. In 1976, the Viking 1 orbiter took a photo of a face on Mars, which turned out to be an optical illusion of shadows on a hill. These claims highlight the delicate balance between philosophy and science. In philosophy, we can conceptually explore our existence and place in the universe. In science, we need hard evidence.

Since its foundation, NASA has been a constant source of support for the development and the launch of observatories designed to figure out if we are alone in the universe. We want to understand if terrestrial planets orbiting other distant stars could harbor life. In December 2021, NASA launched the James Webb Space Telescope (JWST), which is dedicating hundreds of hours to observing these planets to determine whether or not they have atmospheres.

We want to understand if Jupiter's moon Europa has a liquid ocean with more water than all of Earth's oceans combined hidden below its icy surface. In October 2024, NASA launched Europa Clipper, which will determine the thickness of this outer icy layer and characterize the Galilean moon's overall geology.

We want to understand if Saturn's moon Titan has the proper composition to support prebiotic chemistry. In April 2024, NASA approved the Dragonfly mission, a car-sized nuclear-powered drone, to fly over and land on Titan with an estimated 2028 launch. Dragonfly will measure the composition of Titan up close and search for chemical signatures that could indicate the presence of life.

All of these great observatories will help us to understand fundamental truths about celestial bodies. But if we want to answer one of humanity's oldest questions — are we alone? — then we have to be able to communicate our results. Our ability to trust real scientific discoveries is crumbling under the weight of those who want to be "the first," undermining the efforts of thousands of scientists and engineers pursuing truths with due diligence and following the rules of the scientific method we learned in elementary school. When people believe that we have found life on other planets when we have not, we've lost more than public trust — we've lost our own direction.

Flying to Europa or Titan, and looking at the atmospheres of distant exoplanets, are no longer the subject of fantastical science fiction stories. These aren't dreams. This is all of our present-day reality, and even some of our day jobs. When we sit at our desks and analyze data from these observatories, we are inching toward the answer we want so badly. But over-sensationalizing at best — and even outright lying at worst — about the results of these observatories erodes public trust and ultimately harms the very institutions working in the pursuit of scientific discovery.

This comes at a critical time, when the White House has proposed to slash NASA's science budget by nearly 50% and the National Science Foundation's (NSF) budget by up to 50%. Cutting these programs isn't just shortsighted — it's self-destructive. NASA and NSF fund science across all disciplines. Both agencies have long led and participated in global efforts to pursue scientific breakthroughs, like JWST.

Related: The search for alien life

With these proposed budget cuts, we risk losing the scientists and engineers whose research is the foundation for future mission development.

We risk losing the ability to support and train the next generation of scientists.

We risk missing the very voices that could guide us through our most profound discoveries.

We risk losing touch with our fundamental nature to ask and answer questions about our place in the universe.

The search for life beyond Earth has been an ongoing endeavor since the first philosopher questioned if we are alone in the universe. It relies on our ability to connect astronomy, biology, chemistry, physics, engineering, and even philosophy, which initially paved the way for scientific thinking. From all of these angles, we will continue to pursue an answer to this age-old question.

Yet, in our endeavor, we must remember that our mission is greater than the research of the individual. We must not stoop to using over-sensationalized results to support our own personal agendas. And, we must not forget our collective direction: the pursuit of truths and our responsibility to share these truths — and only these truths — with humanity.

Dragonfly, a car-sized, nuclear-powered rotorcraft designed to investigate Titan's potential to host life, passed its Critical Design Review, NASA announced on Thursday (April 24).

"Passing this mission milestone means that Dragonfly's mission design, fabrication, integration and test plans are all approved, and the mission can now turn its attention to the construction of the spacecraft itself," a NASA statement reads.

The $3.35 billion Dragonfly mission was first selected by NASA in 2019 and is being designed and built under the direction of the Johns Hopkins Applied Physics Laboratory (APL) in Maryland, with APL's Elizabeth Turtle as the principal investigator.

The mission has been hit by delays and cost overruns, but studying Titan is considered a high priority by scientists for its potential to harbor alien life.

The mission is set to launch no earlier than July 2028 on a SpaceX Falcon Heavy rocket from NASA's Kennedy Space Center in Florida. The spacecraft will then embark on an almost seven-year-long voyage through deep space to the Saturn system, with the goal of spending more than three years studying areas across Titan's frigid and diverse surface.

Equipped with cameras, sensors and samplers, Dragonfly will assess Titan's habitability, looking out for prebiotic chemistry as well as potential signs of life.

Related: NASA greenlights 2028 launch for epic Dragonfly mission to Saturn's huge moon Titan

Titan is Saturn's largest moon, and the second largest in the solar system behind Ganymede of Jupiter. Its thick, hazy atmosphere shrouds a surface featuring dunes of hydrocarbons and methane lakes. Beneath the moon's icy crust, scientists think there's a subsurface ocean of salty water, adding to the possibilities for Titan to harbor life.

In 2005, NASA's Cassini mission delivered the Huygens probe to Titan. The European Space Agency-built Huygens made a parachute-assisted landing, which provided profound insights into the giant moon. Dragonfly, if successful, could revolutionize our understanding of how life might arise elsewhere in the solar system.

The Extant Life Volumetric Imaging System, or ELVIS, was sponsored by the ISS National Laboratory and developed by researchers at Portland State University (PSU), in partnership with NASA's Jet Propulsion Laboratory in Southern California.

The instrument arrived at the orbiting lab this morning (April 22) on a SpaceX Dragon cargo capsule, which is flying the company's 32nd Commercial Resupply Services mission for NASA.

ELVIS uses cutting-edge holographic technology known as volumetric imaging to create 3D images of microbes and other cells. The mission aims to study how microscopic life adapts to the harsh environment of space; its results could eventually help scientists identify life on other planets and moons, such as Jupiter's Europa and Saturn's Enceladus, team members say.

Related: The search for alien life

Unlike traditional two-dimensional microscopes, ELVIS allows researchers to observe the intricate structure and behavior of living cells in a volumetric format. The system enables detailed biological assessments of how cells change in microgravity — a condition only consistently available to researchers aboard the ISS.

"We are thrilled to leverage the ISS National Lab to prepare ELVIS for its future roles in space exploration missions,” Jay Nadeau, a PSU physics professor and principal investigator on the project, said in a PSU statement.

"The successful operation of ELVIS in the demanding conditions of space not only paves the way for its use in off-Earth environments but also holds implications for enhancing biomedical and microbiological research on our planet," Nadeau added.

Nadeau first proposed using holographic microscopy as a life-hunting technique back in 2017, in a paper arguing that it could potentially detect minute signs of life that regular 2D microscopes might miss.

"It's harder to distinguish between a microbe and a speck of dust than you'd think," Nadeau said in 2017, when she was a research professor of medical engineering and aerospace at the California Institute of Technology in Pasadena.

"Digital holographic microscopy allows you to see and track even the tiniest of motions," she went on to say.

This capability not only allows for possibly identifying microbes among inert matter, as Nadeau and her colleagues proposed in that 2017 paper, but also enables tracking cellular changes that might not be apparent from flat, 2D imaging. ELVIS therefore could see changes induced in a cell's structure in the extreme conditions of space better than a 2D image could.

During its ISS mission, ELVIS will study two Earth-based organisms known for their toughness and resilience: Euglena gracilis, a highly adaptable microalga, and Colwellia psychrerythraea, a cold-loving bacterium found in deep ocean waters. By analyzing these lifeforms in microgravity, scientists aim to uncover both observable and genetic changes that could help life persist in alien environments.

Engineered for space conditions, ELVIS includes durable, low-maintenance components and automation features that reduce the need for astronaut intervention, allowing experiments to run with minimal disruption, mission team members said.

On Earth, large rivers create deltas with sediment-filled wetlands. Deltas form when the mouth of a river empties into another body of water. Besides Earth, Titan is the only planetary body in our solar system with liquid flowing on the surface.

Researchers recently looked for deltas on the big Saturn satellite but came up empty.

"We take it for granted that if you have rivers and sediments, you get deltas," study leader Sam Birch, an assistant professor in the Department of Earth, Environmental and Planetary Sciences at Brown University in Rhode Island, said in a statement.

"But Titan is weird. It's a playground for studying processes we thought we understood," he added.

Related: Titan: Facts about Saturn's largest moon

The researchers were hoping to find deltas on Titan, because these landforms feature lots of sediment. The sediment in deltas tends to come from a large area, and deltas gather it in one place. Studying such sediment could reveal insights about Titan's climate and tectonic histories — and perhaps even possible signs of alien life.

"It's kind of disappointing as a geomorphologist, because deltas should preserve so much of Titan's history," Birch said.

We know that Titan's surface has flowing liquid methane, because NASA's Cassini spacecraft spotted evidence of the stuff on multiple flybys. Cassini used synthetic aperture radar (SAR) to look through Titan's thick atmosphere during these close encounters and found channels and large flat areas that are consistent with large bodies of liquid.

But shallow liquid methane is largely transparent in Cassini's SAR data. Scientists have therefore had a hard time studying Titan's coastal features, because it's hard to make out where the coast ends and the sea floor starts.

So, Birch's team came up with a computer model that simulates what Cassini's SAR would see when looking at Earth. But the model replaced the water in Earth's rivers and oceans with Titan's liquid methane.

"We basically made synthetic SAR images of Earth that assume properties of Titan's liquid instead of Earth's," Birch said. "Once we see SAR images of a landscape we know very well, we can go back to Titan and understand a bit better what we're looking at."

The synthetic SAR images of Earth that they created "resolved large deltas and many other large coastal landscapes," according to the researchers.

They say that new analysis of the Cassini SAR data also revealed other mysteries. For example, Titan's coasts appear to have pits of unknown origin deep within lakes and seas, and deep channels cut across the moon's sea floors offer no clue to how they got there.

"This is really not what we expected," Birch said. "But Titan does this to us a lot. I think that's what makes it such an engaging place to study."

The new study was published in the Journal of Geophysical Research: Planets on March 25.

The team's findings, based on their analysis of James Webb Space Telescope (JWST) data, point to an abundance of dimethyl sulfide (DMS) molecules in the atmosphere of a planet known as K2-18b, which circles its star about 120 light-years from Earth in the Leo constellation. Because DMS is almost exclusively produced by life forms like marine algae on Earth, astronomers consider it a potential "biosignature" in the search for life — past or present — elsewhere in the universe. According to Nikku Madhusudhan of the University of Cambridge and his colleagues, the best explanation for the presence of these molecules — DMS and its chemical cousin dimethyl disulfide, or DMDS, which is also a potential biosignature — on K2-18b is therefore that the planet could be an ocean world "teeming with life."

"These are the first hints we are seeing of an alien world that is possibly inhabited," Madhusudhan told reporters in a press briefing. "This is a revolutionary moment."

However, the excitement sparked by the announcement was quickly tempered by a wave of caution, with scientists emphasizing that the results are still preliminary and come with several caveats. Chief among them is the fact that Madhusudhan and his team reported their DMS detection with a three-sigma statistical significance, indicating a 0.3% chance of it being due to random chance. Experts point out that this falls short of the typical five-sigma standard required for a scientific discovery to minimize false positives, which translates to a 0.00003% chance that the findings are due to a statistical fluke.

Additionally, the data gathered for the new K2-18b study seems to push the JWST to its limits, and critics say the researchers might have used a biased model that effectively artificially inflated the significance of DMS wafting in the planet's atmosphere.

"Concluding that DMS has been detected appears to be premature," Manasvi Lingam, an astrobiologist at the Florida Institute of Technology, who wasn’t involved in the new research, told Space.com. The latest research "involves new data, but until that data has been analyzed independently by others, we cannot make any claims about K2-18b's habitability and the possible existence of life."

Eddie Schwieterman, an assistant professor of astrobiology at the University of California, Riverside, who was not involved with the new research, said he was particularly surprised that ethane wasn't found alongside the possible DMS or DMDS signal. The host star's UV radiation should break down the molecules and form abundant ethane as a byproduct, he explained, meaning its absence in Madhusudhan's data doesn't align with scientists' understanding of planetary atmospheres.

"Either our models are in error, or the DMS/DMDS might not exist," Schwieterman told Space.com. "Finding life outside the solar system won't be a 'one and done' detection — along the way, we should expect some false alarms and this may be one."

Fresh eyes on old data

Madhusudhan and his colleagues first reported a possible DMS detection on K2-18b in 2023, using the JWST then as well. That finding met its own share of skepticism, and was not upheld by independent analyses of the same data. However, this latest study utilized a different JWST instrument and analyzed the planet at different wavelengths, which the research team claims provides a stronger and clearer indication of DMS/DMDS molecules.

Still, many scientists are once again injecting doses of skepticism on the high-profile claim, emphasizing the need for rigorous scientific scrutiny because there is potential for more ordinary, non-biological explanations for the sought-after molecule in K2-18b's atmosphere.

Christopher Glein, a planetary scientist at the Southwest Research Institute in Texas who was not involved with the new study, said his reaction to the announcement "is one of interest but restraint."

"We need to resist the temptation to find a smoking gun," he told Space.com. "The search for life is hard. For a convincing case to be made, multiple self-consistent lines of evidence will need to be assembled."

Other critics argue Madhusudhan and his team engaged in "statistical hacking" by building a selective model where DMS and DMDS are the only explanations for half of K2-18b's atmospheric light spectrum, thereby artificially boosting the molecules' significance.

"Reproducibility is a hallmark of science. We need to see that moving forward," said Glein. "Did they find a needle in the haystack, or just a sharp piece of hay?"

Echoes of life or lifeless chemistry?

Before a planet can be inhabited, it must be habitable.

In 2021, K2-18b's initial atmospheric composition had led Madhusudhan and his colleagues to suggest the planet harbors a warm ocean blanketed by a hydrogen-rich atmosphere. Key to that conclusion was the detection of carbon dioxide, or CO2, in the planet's atmosphere, which led the team to suggest the world is potentially capable of hosting microbial life.

However, more recent studies have questioned that CO2 calculation, raising the possibility that the planet may be too close to its star to support stable liquid water on its surface.

"As much as we want it to be, I am not sure that K2-18b is habitable," said Glein.

Scientists are also at a very early stage in understanding the chemistry of sub-Neptune exoplanets like K2-18b, he said, which means we aren't so sure yet what the abiotic background, or non-biological composition, of these worlds should look like. "These things take time — we've learned in recent years that an anomaly does not necessarily mean life," said Glein.

Matt Genge, a planetary scientist at the Imperial College London, who was not part of the new research, noted that more context and possible formation pathways are needed to explain the abundance of detected molecules in the planet's atmosphere before scientists can confidently attribute the signal to life rather than non-living chemistry or geology.

"When a discovery is as monumental as the discovery of alien life, the bar is set very high for convincing evidence," said Genge. "As a geologist who studies planets, I question the assumption that these molecules can only be produced by life."

If future observations determine that DMS or DMDS is indeed present in the planet's atmosphere, "then it's possible we might be seeing evidence of some cool chemistry rather than biochemistry," said Glein. "As Carl Sagan used to say, life is the hypothesis of last resort."

There is also disagreement about whether DMS should even be considered a reliable biosignature, astrobiologist Michaela Musilova, who was also not involved in the new research, told Space.com. A recent study suggested atmospheric interactions between UV radiation, methane and hydrogen sulfide could lead to a buildup of DMS and DMDS in the upper atmosphere of an otherwise inhospitable world.

Traces of DMS have also been detected on a cold comet devoid of life, which "suggests that these types of molecules could be produced by chemical processes that we are not yet familiar with," said Musilova.

"Until findings are confirmed by multiple teams and through multiple methods, everything directly related to biosignatures and detecting alien life remains, for me, in the 'potential discovery' category," she added.

The search for extraterrestrial life is sprinkled with tantalizing hints that have often ultimately turned out to have non-biological explanations. For instance, a potential signal of phosphine — also considered a possible biosignature — in the clouds of Venus ended up being a false alarm. The complexity of exoplanetary atmospheres and the limitations of current observational technology mean that interpreting signals from light-years away is a delicate and challenging process.

Even if K2-18b doesn't ultimately prove to host life, the techniques and insights gained from studying it will be useful for future investigations of other potentially habitable worlds, said Musilova. "Every new set of data in the astrobiology field is valuable and it can help us advance towards better understanding whether alien life exists elsewhere in the universe and how our life came to be on Earth."

"I just want to make sure that we balance our enthusiasm with a proper dose of patience," said Glein. "It's going to be a fun ride, but we should fasten our seatbelts."

In 2023, researchers using NASA's James Webb Space Telescope (JWST) reported the potential presence of dimethyl sulfide (DMS) on K2-18b, which is nearly nine times more massive than Earth and circles in the "habitable zone" of a star about 120 light-years away from us.

Here on Earth, DMS is produced primarily by life — most prolifically by phytoplankton and other marine microbes — so the 2023 study was met with some enthusiasm. The excitement was tempered, however, by the preliminary nature of the find; JWST's observations were consistent with the presence of DMS but did not confirm it. So the study team looked again, but in a slightly different way this time.

JWST can probe exoplanet atmospheres when these worlds "transit," or cross the face of, their host stars from the observatory's perspective: The telescope detects certain molecules in the air based on the wavelengths of starlight that they absorb.

Related: Does exoplanet K2-18b host alien life or not? Here's why the debate continues

The team made the original, tentative DMS detection using JWST's NIRISS (Near-Infrared Imager and Slitless Spectrograph) and NIRSpec (Near-Infrared Spectrograph) instruments. For the new study, the researchers employed the $10 billion telescope's Mid-Infrared Instrument (MIRI), which scrutinizes different wavelengths of light.

MIRI also detected the fingerprint of DMS (and/or dimethyl disulfide, or DMDS, a close chemical cousin and also a potential biosignature), the researchers report in the new study, which was published online today (April 17) in The Astrophysical Journal Letters.

"This is an independent line of evidence, using a different instrument than we did before and a different wavelength range of light, where there is no overlap with the previous observations," Nikku Madhusudhan, a professor at Cambridge University's Institute of Astronomy, who led both K2-18b studies, said in a statement today. "The signal came through strong and clear."

Based on its size and other characteristics, astronomers suspect that K2-18b may be a "Hycean" world — a class of exoplanet proposed in 2021 that has a huge liquid-water ocean and a hydrogen-rich atmosphere. ("Hycean" is a portmanteau of "hydrogen" and "ocean.")

And K2-18b's air is also rich in DMS and/or DMDS, according to the new study. The researchers estimate concentrations of more than 10 parts per million by volume, compared to less than one part per billion for them here on Earth.

"Earlier theoretical work had predicted that high levels of sulfur-based gases like DMS and DMDS are possible on Hycean worlds," Madhusudhan said. "And now we’ve observed it, in line with what was predicted. Given everything we know about this planet, a Hycean world with an ocean that is teeming with life is the scenario that best fits the data we have."

Madhusudhan and his team aren't claiming to have detected alien life; they say that more research is needed to confirm and extend their findings. Other scientists feel the same way — and some are injecting heavier doses of skepticism into the debate around K2-18b and its life-hosting potential.

One of them is astronomer Chris Lintott, who took issue with Madhusudhan's "strong and clear" characterization of the DMS/DMDS signal.

"Meanwhile, the peer-reviewed paper says 'While [the presence of molecules] DMDS and DMS best explains the current observations, their combined significance … is at the lower end of robustness required for scientific evidence," Lintott, an astrophysics professor at the University of Oxford, wrote on the social media site BlueSky yesterday (April 16).

Detecting signs of alien life is a tricky business, and confirming them is even tougher — especially on a world like K2-18b, which we won't be able to investigate up close for the foreseeable future, if ever. So we should expect the debate, and the data collection, to continue.

A new study backs up that idea — but with a twist. Yes, alien life could be there, researchers say, but probably not in the abundance we once hoped.

"We focus on what makes Titan unique when compared to other icy moons: its plentiful organic content," study co-lead author Antonin Affholder, a postdoctoral research associate in the University of Arizona's Department of Ecology and Evolutionary Biology, said in a statement. "There has been this sense that because Titan has such abundant organics, there is no shortage of food sources that could sustain life."

NASA's Cassini mission flew past Titan over 100 times, and in 2005, the European ride-along probe Huygens landed on its surface. On its way down, Huygens collected valuable data on Titan's dense atmosphere, finding a host of photochemical reactions — light-driven chemical reactions that shape the moon's chemical environment and could play a role in making it potentially habitable. This is because such reactions can create complex organic molecules, including some that could be the building blocks for life.

Related: Titan: Facts about Saturn's largest moon

The idea is that these organic molecules eventually settle on Titan's surface and, through a mix of material exchange and possible geochemical processes, find their way down into the moon's hidden ocean — potentially making the dark waters below a habitable environment.

But "potentially" is a key word here, according to the new study.

"We point out that not all of these organic molecules may constitute food sources, the ocean is really big, and there's limited exchange between the ocean and the surface, where all those organics are, so we argue for a more nuanced approach," said Affholder.

Using bioenergetic modeling — a method that uses mathematical simulations to quantify the energy needed to make and break chemical bonds in a biological system — the team attempted to identify a plausible scenario in which life could emerge on Titan. They landed on a simple and familiar process: fermentation.

"Fermentation probably evolved early in the history of Earth's life and does not require us to open any door into unknown or speculative mechanisms that may or may not have happened on Titan," Affholder said.

Fermentation is a simple metabolic process in which microorganisms, such as bacteria, break down organic molecules like sugars or carbohydrates into simpler compounds. The key part? It all happens without oxygen, which makes it especially relevant for a world like Titan, where oxygen is scarce or absent.

"We asked, could similar microbes exist on Titan?" Affholder said. "If so, what potential does Titan's subsurface ocean have for a biosphere feeding off of the seemingly vast inventory of abiotic organic molecules synthesized in Titan's atmosphere, accumulating at its surface and present in the core?"

Using the simplest of all known amino acids — glycine, which is relatively abundant throughout the solar system — the team's simulations found that conditions on Titan could, in theory, support microbial life through fermentation. However, only a tiny portion of Titan's organic material might actually reach the ocean, depending on how much glycine makes its way down from the surface.

"This supply may only be sufficient to sustain a very small population of microbes weighing a total of only a few kilograms at most — equivalent to the mass of a small dog," Affholder said.

"Such a tiny biosphere would average less than one cell per liter of water over Titan's entire vast ocean," he added. "We conclude that Titan's uniquely rich organic inventory may not in fact be available to play the role in the moon's habitability to the extent one might intuitively think."

That means that, if life does exist on Titan, it could be extremely sparse, making it especially challenging for future missions to detect — like trying to find a needle in a haystack, the team concludes.

The new study was published April 7 in The Planetary Science Journal.

"A simple positive detection would change everything," said astronomer Daniel Angerhausen of ETH Zurich in Switzerland in a statement. "But even if we don't detect life, we'll quantify how rare – or common – planets with detectable biosignatures really might be."

LIFE, the Large Interferometer For Exoplanets, is a proposal for an ambitious new mission designed to reveal how many Earth-like planets out there are inhabited by some form of life. Here's the plan.

Led by ETH Zurich astronomers, the mission concept proposes for four space telescopes to fly in formation around a central "combiner" spacecraft. The idea is that the four space telescopes would fly tens to hundreds of meters apart and collectively act as an interferometer, meaning they'd combine their light detections by feeding signals to the central combiner spacecraft. Furthermore, to block out the glare of a star so that LIFE could detect orbiting exoplanets, the telescopes will employ a technique known as "nulling interferometry," whereby the light of the star is combined "out of phase." This would allow what's known as "destructive interference" to cancel out that light, leaving behind just the light given off by orbiting planets.

LIFE won't be able to directly image exoplanets, but by observing in the mid-infrared it will be able to spectroscopically measure their light and reveal which molecules are present in their atmospheres (if they have one).

LIFE will target dozens of Earth-size planets in the habitable zone of their stars, in the hopes of finding biosignatures, which are atmospheric gases produced, or kept in balance, by life. The likes of oxygen and water vapor are the most obvious of such biosignatures, but others include ozone, methane, nitrous oxide, dimethyl sulphide and phosphine, to name a few.

Currently, however, LIFE is just a concept. It has not yet been adopted by a space agency.

Still, Angerhausen and colleagues at ETH Zurich wanted to find out how much LIFE could tell us, even if it failed to find biosignatures. What would a negative or null result imply about the frequency of inhabited planets in the galaxy? For this, they turned to statistics.

So before we go any further, we also need to delve into the world of statistics to understand their conclusions.

The team employed a Bayesian statistical model to find the smallest number of exoplanets LIFE would need to observe to yield a firm answer as to how common inhabited worlds are. Bayesian statistics has to do with finding the probability of an outcome based on other probabilities that we already know (these are described as "priors"). Bayesian statistics describes the level of confidence or belief we have that an event will occur based on what we know about a certain situation.

For a mundane example, suppose you hear a loud bang. Was it thunder? Maybe a firework? Bayesian statistics allows you to deduce the answer based on the probabilities of the priors, such as knowing whether fireworks are usually set off around certain times of the year (like New Year's Eve, the fourth July in the United States and Bonfire Night in the U.K.) or if the weather has been forecast to be stormy. Based on these priors, Bayesian statistics allows you to quantify your belief as to whether it was thunder or a firework.

In contrast to Bayesian statistics, an alternative way of looking at probabilities is "frequentist statistics." As the name implies, this describes the probability of an outcome based on the frequency of that event occurring after many trials.

Unlike Bayesian statistics, frequentist statistics does not concern itself with priors. When tossing a coin, frequentist statistics doesn't worry about whether the previous four tosses have all landed on heads. Assuming an unbiased coin, the chances of it landing on heads or tails is always 50%, and over a high enough number of trials this 50% probability would appear readily apparent in the data.

So, back to the question: how many planets could LIFE observe and not find any biosignatures before astronomers can start drawing conclusions regarding the prevalence of life in the galaxy? Through the use of Bayesian statistics, Angerhausen's team found that between just 40 and 80 exoplanets would need to be observed with no detectable biosignatures to conclude with confidence that fewer than 10 to 20% of similar planets in the universe has life. Surveying this many exoplanets is well within LIFE's planned abilities.

If LIFE detects no biosignatures on its sample of planets, it cannot conclude that there is no life anywhere, but it can place a maximum limit on how many planets in the galaxy do have life. And, as the sample size increases, if there continues to be no detection, then that maximum number would decrease further. In other words, LIFE could tell us whether inhabited planets are rare or not.

There will be uncertainties, however. Perhaps a biosignature will be missed — after all, some of these gases are not easy to detect. Or perhaps some planets will be mistakenly included in the sample of potentially habitable planets when, in fact, they do not fit the requirements to be considered potentially habitable in the first place. Again, this could occur because observations are difficult.

"It's not just about how many planets we observe, it's about asking the right questions and how confident we can be in seeing or not seeing what we’re searching for," said Angerhausen. "If we're not careful and are overconfident in our abilities to identify life, even a large survey could lead to misleading results."

To test their conclusion, Angerhausen and colleagues also applied frequentist statistics to the problem. They found the results to be similar.

"Slight variations in a survey's scientific goals may require different statistical methods to provide a reliable and precise answer," said Emily Garvin, a Ph.D. student at ETH Zurich. "We wanted to show how distinct approaches provide a complementary understanding of the same dataset, and in this way present a roadmap for adopting different frameworks."

With luck, if the LIFE mission or something similar ever goes ahead, it will find a planet, or planets, with life of some variety. But even if it doesn't, the results could still be profound and take us one giant leap closer to understanding our place in the universe.

The study was published on April 7 in The Astronomical Journal.

Those potential signs of life are a group of chemicals called methyl halides, which on Earth are produced by some bacteria and ocean algae.

"Unlike an Earth-like planet, where atmospheric noise and telescope limitations make it difficult to detect biosignatures, hycean planets offer a much clearer signal," said Eddie Schwieterman, who is an astrobiologist at the University of California, Riverside, in a statement.

For now, the existence of hycean planets remains hypothetical. Their name is a portmanteau of "hydrogen" and "ocean," first coined in 2021 by planetary scientist Nikku Madhusudhan of the University of Cambridge.

Related: 'Hycean' exoplanets may not be able to support life after all

Hycean planets are expected to orbit red dwarf stars, and the best candidate for a hycean world is the planet K2-18b. This exoplanet, which is categorized as a "sub-Neptune" world, orbits in the habitable zone of a red dwarf star 124 light-years from Earth in the constellation of Leo, the Lion.

The Hubble Space Telescope discovered water vapor in K2-18b's atmosphere in 2019, and JWST has detected the presence of carbon dioxide and methane in the planet's atmosphere, along with a lack of carbon monoxide and ammonia — exactly as predicted by the hycean planet hypothesis. There's also tentative evidence that a compound called dimethyl sulfide, which on Earth is only produced by ocean plankton, also exists in K2-18b's atmosphere, but this evidence continues to prove contentious.

Now a team of researchers at the University of California, Riverside and ETH Zurich in Switzerland have gone a step further. They propose that another family of compounds called methyl halides, generated by microbial ocean life on Earth, could produce a biosignature — that is, a chemical signature of biological life — in the atmosphere of a hycean world that's more easily detectable than the signature of oxygen is on an Earth-like planet.

"Oxygen is currently difficult or impossible to detect on an Earth-like planet," said Michaela Leung of the University of California, Riverside, the first author of a new paper describing the research. "However, methyl halides on hycean worlds offer a unique opportunity for detection with existing technology."

Methyl halides are molecules that incorporate carbon atoms and three hydrogen atoms attached to a halogen atom such as bromine, chlorine or fluorine. (Halogens are group of reactive, non-metallic elements.) On Earth, methyl halides are produced by life, but they are far from abundant in our planet's atmosphere.

On hycean worlds, however, things could be different. Leung's team suspect that the conditions on such worlds, should they exist, would allow methyl halides to accumulate in large quantities in the atmosphere. Furthermore, methyl halides would have strong absorption features in infrared light, at the same wavelengths that the JWST is designed to observe.

"One of the great benefits of looking for methyl halides is, you could potentially find them in as few as 13 hours with James Webb. That is similar or lower, by a lot, to how much telescope time you'd need to find gases like oxygen or methane," said Leung. "Less time with the telescope means it's less expensive."

Related: The search for alien life

There are two caveats to what Leung's team propose. One is that we don't yet know whether hycean worlds actually exist. They were proposed as a possibility to explain certain properties of some warm sub-Neptune-type planets that have average densities that imply a thick hydrogen atmosphere and a deep ocean of liquid water. However, directly observing an ocean beneath such a world's hydrogen envelope is not currently feasible.

The second issue is that we don't know if such oceans could be habitable. A hycean world would be hot, and although the extreme conditions beneath the hydrogen envelope would prevent the ocean from evaporating, it is uncertain whether it would be too hot for life as we know it. However, a positive detection of methyl halides in the atmosphere of a candidate hycean world would be a strong indication that life could exist there in a deep ocean.

If life does exist on such a world, it would have to breathe hydrogen, not oxygen.

"These microbes, if we found them, would be anaerobic," said Schwieterman. "They'd be adapted to a very different type of environment, and we can't really conceive of what that looks like, except to say that these gases are a plausible output from their metabolism."

Anaerobic life — i.e., lifeforms making do without oxygen — exist on Earth, so it wouldn't be truly alien to life on our planet, even if the environment that it would live in is. Earth-like worlds orbiting red dwarfs could be in short supply, since red dwarfs are fierce little beasts, prone to unleashing bursts of harsh radiation that can strip away the atmosphere of an Earth-like planet. However, hycean worlds protected by their thick hydrogen atmospheres might be less vulnerable to attack from their star.

It could therefore be that hycean worlds are where life resides in red dwarf systems, and since red dwarfs make up about three-quarters of all stars in our Milky Way galaxy, there could be many more habitable hycean worlds in the cosmos than Earth-like worlds.

The research by Leung's team was published on March 11 in The Astrophysical Journal Letters.

As some of the most energetic phenomena in the universe, supernovae occurring within 60 light-years of Earth could have stripped our planet's atmosphere of its protective ozone layer, exposing life to damaging ultraviolet radiation from the sun, a team of astronomers has discovered.

"A slightly more distant supernova could still cause considerable loss of life, but at this distance, it would be terrifying," study co-author Nick Wright, an astrophysics professor at Keele University in England, told Space.com via email.

Wright and his team used data on the locations of stars collected by the now-retired Gaia satellite to conduct a virtual census of more than 24,000 of the most luminous stars in the universe. They focused on those located within 3,260 light-years of the sun to identify new groups of young, massive stars and reconstruct nearby star formation history.

"It was only once we had completed the work that we realized we could also use the sample to estimate the supernova rate," said Wright. "When we’d done that, we realized it was very close to the rate of unexplained mass extinction events on Earth!"

Supernovas alligning with extinction events

Wright and his team found the timing of supernovae near Earth aligned with two significant mass extinction events on our planet: the late Devonian, a series of mass extinction events that occurred 372 million years ago, and the Ordovician, which occurred 445 million years ago and was the first of the big five mass extinction events in our planet's history.

75% of all species, particularly in the types of fish found in ancient seas and lakes, while the Ordovician event wiped out about 85% of marine species.

"It surprised me that the two rates were so similar, which made us want to highlight it," said Wright.

Previous research has found evidence of an influx of the radioactive isotope iron-60 in cosmic dust collected from the Antarctic snow and from the surface of the moon, which can only be attributed to interstellar sources like supernovae. Various studies have linked this flux to the depletion of Earth's ozone layer, caused by cosmic rays showered onto our planet by the stars' explosive deaths.

"Supernovae produce a very high flux of high-energy radiation, which when it reaches the Earth could cause considerable destruction, including breaking apart the ozone molecules that make up the ozone layer," Wright told Space.com.

This ozone depletion, in turn, is thought to have contributed to at least one widespread extinction of marine mammals, seabirds, turtles, and sharks that occurred around 2.6 million years ago. The primary cause behind the Devonian and Ordovician mass extinction events is not fully understood, but both of them have also been linked to the depletion of Earth's ozone layer.

The new study's simulations showed roughly one to two supernovae occur each century in galaxies like the Milky Way.

Within 60 light-years of Earth — the typical distance at which a supernova could potentially cause catastrophic destruction to life on Earth — the rate of supernovae was 2 to 2.5 per billion years. This estimate is in good agreement with the number of unexplained mass extinction events on Earth — specifically, the Devonian and Ordovician extinctions, both of which occurred within the last billion years — raising the possibility that nearby supernovae may have contributed to these events, according to the study.

"It’s worth noting that we don’t have proof that those extinctions were definitely caused by supernovae, only that the rates match up, and therefore, it seems very plausible," Wright said.

These findings are "a great illustration for how massive stars can act as both creators and destructors of life," Alexis Quintana of the University of Alicante in Spain, who led the new study, said in a statement.

"Supernova explosions bring heavy chemical elements into the interstellar medium, which are then used to form new stars and planets," she said. "But if a planet, including the Earth, is located too close to this kind of event, this can have devastating effects."

The team's research was published on Tuesday (March 18) in the journal Monthly Notices of the Royal Astronomical Society.

That's the conclusion of Florida Institute of Technology researcher Caldon Whyte, who's particularly fascinated by these stellar remnants. Until now, scientists have generally thought that planets orbiting white dwarfs would be unsuitable for life because the dynamic temperature decrease of their dead parent star makes their atmospheres too unstable.

As the James Webb Space Telescope (JWST) increasingly investigates white dwarf systems, however, Whyte and colleagues developed a model capable of assessing if two key life-sustaining processes could occur in the range of orbits around a white dwarf temperate enough to allow liquid water to exist. This region around stars is referred to as the habitable zone or Goldilocks zone, because it's neither too hot nor too cold, just like the bear's porridge in the famous story.

The model developed by the team found that white dwarfs can fuel both processes simultaneously, making Earth-like planets possible around white dwarfs.

This discovery could help widen the focus of our search for life elsewhere in the cosmos, suggesting that systems that had previously been written off need to be revisited.

Related: The search for alien life

Expanding the boundary of Goldilocks zones

Habitable zones around stars are usually easy to define for stellar bodies like the sun and other main-sequence stars, which tend to have fairly stable temperatures over long periods of time. That isn't the case with white dwarfs, which form when stars like the sun run out of fuel for nuclear fusion, shedding their outer layers as their cores collapse and forming a cooling stellar ember.

Because these late-stage stellar bodies no longer have a source of fuel, they spend the rest of their existence gradually cooling, and that makes their temperatures and energy outputs inconsistent.

As a result, the Goldilocks zones around white dwarfs are constantly narrowing, with the distance that liquid water can exist without freezing on orbiting planets constantly shrinking around these dead stars.

Whyte and colleagues wanted to know if a planet orbiting a white dwarf in a constricting habitable zone could sustain processes that seem to be important for life for a period of seven billion years, the stretch that scientists have estimated is the maximum habitable lifetime of an Earth-like planet in this region around a star.

The team's model focused on two processes: photosynthesis, which plants use on Earth to convert sunlight, water and carbon dioxide into sugars, and ultraviolet (UV)-driven abiogenesis. This is the idea that UV radiation could help life arise — one of the theories that has been suggested to explain life taking root on Earth.

The model simulated an Earth-like planet orbiting a white dwarf, allowing the team to measure how much energy the world received as its dead star cooled and the habitable zone it sat in shrank.

Surprisingly, this revealed that, over the seven billion years, the simulated planet received enough energy to sustain both photosynthesis and UV-driven abiogenesis.

"That isn’t really common around most stars," Whyte said in a statement. “Something like the sun, of course, can provide enough energy, but brown dwarfs and red dwarfs smaller than the sun don’t really provide the energy in the UV and the photosynthesis range."

These findings could help scientists decide which systems to focus telescopes like the JWST on as humanity continues to search the cosmos for alien life. In particular, the results suggest that white dwarf systems may be worth a look as this hunt continues.

"We're giving them the confidence that these star systems are worth investing time and money into," Whyte said.

The team's results were published in December 2024 The Astrophysical Journal Letters.

NASA announced in July of last year that the rock, found in Mars' Jezero Crater by the agency's Perseverance rover, held some of the best evidence yet that ancient microbial life may have existed on the Red Planet billions of years ago, when it was significantly wetter than it is today. Earlier this week, scientists involved with the discovery presented their findings publicly for the first time this week at the Lunar and Planetary Science Conference in Texas, detailing the rock's chemical signatures and structures that continue to offer tantalizing hints of ancient Martian microbial life.

The fine-grained mudstone named Cheyava Falls, after the highest waterfall in Arizona's Grand Canyon, sits at the edge of an ancient river valley known as Neretva Vallis, which runs along the inner wall of the crater. The rock features spots of black, blue, or greenish hues, which the researchers have nicknamed "poppy seeds." Alongside these are dozens of dark-rimmed, millimeter-size splotches dubbed "leopard spots." Perseverance's instruments have revealed that several rocks hosting these two features are rich in iron, but that they vary in their oxidation states and redness — a telltale sign of activity by organic matter, which may have bleached the rocks of their red color.

"On Earth, reactions like these are commonly associated with microbially-driven organic matter respiration," Joel Hurowitz, the deputy principal investigator of the PIXL instrument located at the end of Perseverance's robotic arm, said at the conference.

Back in July, the discovery team had also noted the presence of calcium sulfate veins running through the rock, suggesting that water may have once flowed through it. While this and other features could point to non-biological processes, such as exposure to high temperatures from a volcanic event, ongoing analysis suggests the rock was never subjected to such heat or exposed to heat-related processes that would have caused it to recrystallize. "Everything seems to be consistent with low-temperature processes," Hurowitz said.

Scientists suspect the Neretva Vallis channel was carved out eons ago, by water gushing into the crater. One theory is that mud loaded with organic compounds was deposited into the valley, later cementing into the Cheyava Falls rock. Alternatively, a second water episode could have seeped into the rock after it had already formed, creating the features observed. "The rocks that we investigated appear to fill the Neretva Vallis channel," Hurowitz said.

There are no life-detection instruments onboard Perseverance, as its mission is to collect samples of scientific interest that will be returned to Earth for further scrutiny.

"As a community, we should feel compelled to do a whole lot of laboratory, field and modeling studies to try to investigate features like this in more detail," Hurowitz said. "And ultimately bring these samples back home so that we can reach a conclusion with regard to whether they were or were not formed by life."

However, details of the troubled Mars Sample Return effort remain uncertain after costs that ballooned to $11 billion led NASA to overhaul its approach and seek new ideas from its research centers, private industry and academia.

Former NASA administrator Bill Nelson announced earlier this year that the agency is leaving two options for the Trump administration to return to Earth 30 cigar-sized tubes containing bits of Mars that Perseverance has been collecting since 2021, including the Cheyava Falls sample. The two approaches differ in the way they would put hardware down on Mars, but either would require Congress to allocate $300 million to the mission for it to start launch proceedings by 2030 and return the samples between 2035 and 2039.

Scientists are eager to analyze the Cheyava Falls sample, as it could help answer one of humanity’s most profound questions: Are we alone in the universe?

"The discovery of life beyond Earth is so profound, so paradigm-shifting, you have to get it right," Amy Williams, an astrobiologist at the University of Florida who's on the Perseverance science team, had told Space.com shortly after the discovery. "Once you cross that line, you can't come back."

We don’t know for sure, but the answer is inextricably linked to the moment when water first materialized in the cosmos — and new simulations suggest the very first generation of stars helped form such life-giving water just 100 million to 200 million years after the Big Bang. This pushes back previous estimates by more than 500 million years.

"We were surprised that water could actually form so early on — even before the birth of the first galaxies," study co-author Muhammad Latif of the United Arab Emirates University told Space.com. The findings suggest that if some of this initial reservoir of water survived the heat-filled chaos of early galaxy formation, it could have been absorbed into newborn planets, potentially leading to habitable, water-rich worlds just a couple hundred million years after the Big Bang. "It's all connected with the story of how early life can start in the universe," Latif said.

Previous observations from the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile suggested that water existed about 780 million years after the Big Bang, when the young universe was chock-full of lightweight hydrogen and helium along with small amounts of lithium. These elements formed the first generation of stars, known to astronomers as Population III stars, which were enormous — up to dozens or even hundreds of times the mass of our sun — and lived notably short lives before dying as supernovas. Many of the universe's heavier elements, including oxygen, were forged within these stars through nuclear reactions and dispensed into space upon their deaths, where they were later incorporated into the next generation of stars.

To determine when water first formed in the universe, Latif and his colleagues used numerical models to trace the life cycles of two first-generation stars: one was 13 times heavier than our sun, and the other was 200 times heavier than our star. The smaller virtual star lived for 12.2 million years before dying in an explosive supernova, dumping about 0.051 solar masses of oxygen (nearly 17,000 Earth masses) into its surrounding space. The larger simulated star burned through its fuel in just 2.6 million years before meeting its own explosive end, showering a whopping 55 solar masses of oxygen (more than 18 million Earth masses) into space.

The simulations revealed that as shockwaves from each supernova radiated outward, turbulent density fluctuations created ripples that led some of the gas to coalesce into dense clumps. These leftover clumps, enriched by metals including oxygen ejected by supernovas, were likely the primary sites for water to form across the early universe.

Nestled within denser parts of the clouds, the water would have been protected from being destroyed by harsh radiation from nearby stars, Latif said. However, his team considered the simplest case of just one star forming in each clump, whereas theoretical simulations suggest multiple star systems to be the norm; more than half of all stars in the sky have one or more siblings. Multiple nearby stars would mean more dense, water-enriched clumps, but also a lot more radiation, which "might change a few things, but we still expect water might to survive," said Latif. "These are the first questions that we tried to answer, but we need more people to be working on this topic and explore this in more detail."

Follow-up simulations by his team suggest these water-harboring clumps are also favorable sites for habitable worlds to coalesce. Whether water within these clumps could have persisted through billions of years of cosmic evolution, and if so, how, is not yet fully understood. One leading theory suggests comets may have delivered water to Earth, but any such icy transporters from the early universe are not expected to have survived the harsh conditions of the Epoch of Reionization, said Latif, referring to a period about 400,000 years after the Big Bang when ionizing ultraviolet light from the first stars and galaxies pervaded the universe and lifted the primordial cosmic fog. However, the researchers are not yet ruling out the possibility that at least some of the water on Earth may be primordial in origin.

Populations of water-rich planets in the early universe would create faint emissions, Latif said, which could potentially be detected in the coming decade by ALMA or the forthcoming Square Kilometer Array in Australia and South Africa. If such emissions are indeed observed, it would be a "game changer," he said, in that it would shift the paradigm of origin of life to within just a couple hundred million years after the Big Bang.

"It opens a whole new line of research."

The study was published on Monday (March 3) in the journal Nature Astronomy.

New telescope technologies, including space-based tools such as the James Webb Telescope, have enabled us to discover thousands of potentially habitable exoplanets that could support life similar to that on Earth.

Gravitational wave detectors have opened a new avenue for space exploration by detecting space-time distortions caused by black holes and supernovae millions of light-years away.

Commercial space ventures have further accelerated these advancements, leading to increasingly sophisticated spacecraft and reusable rockets, signifying a new era in space exploration.

NASA’s OSIRIS-REx mission successfully touched down on asteroid Bennu when it was 207 million miles away from Earth and brought back rock and dust samples.

Several countries have developed the ability to deploy robots on the moon and Mars, with plans to send humans to these celestial bodies in the future.

A central driver of all these ambitious endeavours is still that fundamental question of whether life exists — or ever existed — elsewhere in the universe.

Defining life

Defining life is surprisingly challenging. While we intuitively recognize living organisms as having life, a precise definition remains elusive. Dictionaries offer various descriptions, such as the ability to grow, reproduce and respond to stimuli.

But, even these definitions can be ambiguous.

A more comprehensive definition considers life as a self-sustaining chemical system capable of processing information and maintaining a state of low entropy with little disorder or randomness.

Living things constantly require energy to sustain their molecular organization and maintain their highly organized structures and functions. Without this energy, life would quickly descend into chaos and disrepair. This definition encompasses the dynamic and complex nature of life, emphasizing its ability to adapt and evolve.

Life on Earth, as we currently understand it, is based on the interplay of DNA, RNA and proteins. DNA serves as the blueprint of life, containing the genetic instructions necessary for an organism’s development, survival and reproduction. These instructions are converted into messages that guide the production of proteins, the workhorses of the cell that are responsible for a vast array of functions.

This intricate system of DNA replication, protein synthesis and cellular processes — all based on long strings of molecules linked by carbon atoms — is fundamental to life on Earth. However, the universe may harbour life forms based on entirely different principles and biochemistries.

Something other than carbon

Life elsewhere could use different elements as building blocks. Silicon, with its chemical similarities to carbon, has been proposed as a potential alternative.

If they exist, silicon-based life forms may exhibit unique characteristics and adaptations. For instance, they might use silicon-based structures for support, analogous to bones or shells in carbon-based organisms.

Even though silicon-based organisms have not yet been found on Earth, silicon plays an important role in many existing life forms. It is an important secondary component for many plants and animals, serving structural and functional roles. For example, diatoms, a type of algae found in the ocean, feature glassy cell walls made of transparent silicon dioxide.

This doesn’t make diatoms silicon-based life forms, but it does prove silicon can indeed act as a building block of a living organism. But we still don’t know if silicon-based life forms exist at all, or what they would look like.

The origins of life on Earth

There are competing hypotheses on how life arose on Earth. One is that life’s building blocks were delivered on or in meteorites. The other is that those building blocks came together spontaneously via geochemistry in our planet’s early environment.

Meteorites have indeed been found to carry organic molecules, including amino acids, which are essential for life. It’s possible that organic molecules formed in deep space and were then brought to Earth by meteorites and asteroids.

On the other hand, geochemical processes on early Earth, such as those occurring in warm little ponds or in hydrothermal vents deep in the ocean, could have also provided the necessary conditions and ingredients for life to emerge.

However, no lab has yet been able to present a comprehensive, certain pathway to the formation of RNA, DNA and the first cellular life on Earth.

Many biological molecules are chiral, meaning they exist in two forms that are mirror images of each other, like left and right hands. While both left- and right-handed molecules are typically naturally produced in equal amounts, recent analyses of meteorites have revealed a slight asymmetry, favouring the left-handed form by as much as 60 percent.

This asymmetry in space-derived organic molecules is also observed in all biomolecules on Earth (proteins, sugars, amino acids, RNA and DNA), suggesting it could have arisen from the slight imbalance delivered from space, supporting the theory that life on Earth is extraterrestrial in origin.

Chances of life

The slight imbalance in chirality observed in many organic molecules could be an indicator that life on Earth originated from the delivery of organic molecules by extraterrestrial life. We could well be descendants of life that originated elsewhere.

The Drake equation, developed by astronomer Frank Drake in 1961, provides a framework for estimating the number of detectable civilizations within our galaxy.

This equation incorporates factors such as the rate of star formation, the fraction of stars with planets and calculates the fraction of those planets where intelligent life may emerge. An optimistic estimate using this formula suggests that 12,500 intelligent alien civilizations might exist in the Milky Way alone.

The primary argument for extraterrestrial life remains probabilistic: considering the sheer number of stars and planets, it seems highly improbable that life wouldn’t have arisen elsewhere.

The probability of humanity being the sole technological civilization in the observable universe is considered to be less than one in 10 billion trillion. Additionally, the chance of a civilization developing on any single habitable planet is better than one in 60 billion.

With an estimated 200 billion trillion stars in the observable universe, the existence of other technological species is highly likely, potentially even within our Milky Way galaxy.

That's the scenario posited by a team led by former University of California (UC) Santa Cruz undergraduate Caitlyn Nojiri.

During her studies of astrophysics, Nojiri became fascinated with cosmic rays, showers of high-energy particles from deep space, and their effects on Earth.

Nojiri cites a 2003 Belgian election that went haywire due to a cosmic ray as one of her early interests. In that case, a cosmic ray is thought to have caused a slight flip in the electronic voting system, incorrectly adding votes to the tally.

"It's insane that something is from space can have that kind of an impact on our electronics," Nojiri told Space.com. "So we're thinking, okay, how does that have a potential impact on other aspects of our life?"

That question initiated her research with UC Santa Cruz professor Enrico Ramirez-Ruiz and postdoctoral fellow Noémie Globus.

"Our project was to model the propagation of cosmic rays from supernova sources to see their potential impacts on life on Earth," Nojiri explained.

A cosmic fishing trip

One particular supernova caught the attention of Nojiri and colleagues.

A study dating iron-60, an isotope of iron that is a byproduct of supernovas, in the seafloor indicated that a nearby supernova likely bombarded the Earth with cosmic rays some 2.5 million years ago.

Simulating the supernova with computer models, the team suggested that the radiation from this stellar explosion pummeled the our planet for around 100,000 years after the event. That radiation was potentially strong enough to break apart DNA.

"But we're not biologists," laughed Nojiri. Thus, the team dug into biology papers to look for clues. And that's when they came across a 2024 study about the cichlids in Lake Tanganyika.

Not only is Lake Tanganyika Africa's largest and deepest lake, but it's also one of the world's 20 most ancient lakes, having formed between 9 million and 12 million years ago.

Lake Tanganyika is perhaps best known by scientists for its incredible biodiversity. More than 2,000 species live in the lake, including some 250 types of cichlids.

With its ancient age and rich biodiversity, Lake Tanganyika is an evolutionary biologist's dream.

That 2003 study indicates that about 2.5 million years ago, cichlids underwent rapid species diversification, which might have impacted virus evolution in the lake, too. This is interesting as Lake Tanganyika's cichlids are disproportionately affected by viruses compared to other fish.

That 2.5-million-year timeframe coincides with Nojiri's supernova, supporting the theory that its DNA-busting radiation might be responsible for the diversity of cichlids and their associated viruses.

"There could have been other factors, but it's definitely interesting," Nojiri pointed out.

Of course, there needs to be far more research to prove this is a case of causation rather than mere correlation, but that research is plausible.

"You could expect to see diversification potentially in other places as well," Nojiri, now looking to continue her studies of astrophysics at the doctoral level, concluded.

So, who's ready for a cosmic fishing trip?

The team's research was published in The Astrophysical Journal Letters.

One of the holy grails of modern astronomy is finding life on an alien planet. But that is an extremely daunting task. The James Webb Space Telescope is unlikely to be able to identify biosignatures — the atmospheric gases produced by life — in any nearby worlds. And the upcoming Habitable Worlds Observatory will be able to scan only a few dozen potentially habitable exoplanets.

One of the big hurdles is that biosignature spectra are usually very weak. So one way to narrow down the list of potential candidates is to focus on the ability of a planet to host life, mainly in the form of water vapor in its atmosphere. If a planet has a lot of water vapor, it might have a good chance of hosting life as well.

This requirement is the basis of the habitable zone, the region around a star where the radiation onto a planet isn't too little that all the water freezes out and isn't too much that the water boils away. In our solar system, Venus is near the inner edge of the habitable zone, and its surface reaches temperatures of over 800 degrees Fahrenheit (427 degrees Celsius) underneath a thick, choking atmosphere. On the opposite end, Mars is essentially frozen out, with all of its water locked up in polar ice caps and under the surface.

But even a search for water has difficulties. For example, from great distances, it's very difficult to tell Earth (inhabited) apart from Venus (uninhabited and outright hostile to life). Their atmospheric spectra are just too similar when you're trying to hunt for water vapor.

In a recent preprint paper, astronomers note that they've found a different signature gas that might be a useful tool for separating uninhabitable worlds from potentially habitable ones: sulfur dioxide.

Warm, wet worlds like Earth have very little sulfur dioxide in their atmospheres. That's because rain can pick up atmospheric sulfur dioxide and wash it down into the oceans or into the soil, essentially cleansing it out of the atmosphere.

And, ironically, planets like Venus also have very little sulfur dioxide. In that planet's case, high amounts of ultraviolet radiation from the sun catalyze reactions that convert sulfur dioxide to hydrogen sulfide in the upper atmosphere. There's still a lot of sulfur dioxide, but it tends to slink down into the lower atmosphere, where it can't be detected.

Thankfully, there's another option: planets around red dwarf stars. Red dwarfs emit very little ultraviolet radiation. So if a dry, uninhabitable planet were to form around a star like that, a lot of sulfur dioxide would persist in its upper atmosphere.

Astronomers are especially interested in the planetary systems of red dwarfs. One reason is that red dwarfs are the most common kind of star in the galaxy. The other is that many nearby systems — like our nearest neighbor, Proxima Centauri, as well as TRAPPIST-1 — are red dwarfs known to host planets. This makes them very appealing targets for upcoming searches for life.

The new technique based on sulfur dioxide can't tell us which planets might host life, but they do tell us which planets probably don't. If we see a rocky planet orbiting a red dwarf and detect an abundance of sulfur dioxide in its atmosphere, it is likely a lot like Venus — a dry, hot world with a thick atmosphere and little to no water. Not a good candidate for life.

But if we fail to see any significant sulfur dioxide, that world is likely a good candidate for a follow-up observation to search for signs of water vapor and, if we're lucky, life.

It's going to take an enormous amount of detective work and dogged determination to find life on another planet. So any clue we can get, even one based on sulfur dioxide to narrow down our list, is welcome.

"We're arguing that intelligent life may not require a series of lucky breaks to exist," said lead author Dan Mills of the University of Munich in a statement. "Humans didn't evolve 'early' or 'late' in Earth's history, but 'on time' when the conditions were in place."

It was the Australian physicist Brandon Carter who first popularized the notion that life on Earth was the result of a sequence of unlikely events, which he described as "hard steps" in a 1983 paper.

A black hole theorist, from time to time Carter also dipped his hand into more existential matters, specializing in drawing assumptions from probabilistic and anthropic (i.e. the argument that conclusions about the nature of the cosmos have to be constrained by the fact that we exist) reasoning to say something about our existence in the universe.

Related: The search for alien life

This is no better seen than in his Doomsday argument, in which Carter posits that we, as individuals, are more likely to exist at a time when the greatest number of humans are alive. For example, imagine every human who ever lived is given a number based on the order in which they were born, and then these numbers are pulled from a pot like the numbers in a lottery — you're more likely to pull a higher number than a very low number if the total number of humans who have lived and will ever live is large. Since population growth can be modeled as exponential, the fact that we exist now with a relatively low birth number compared to all the hundreds of billions to trillions of people who will follow us suggests that something catastrophic could be about to happen to the human race that will curtail future population numbers. At least, that's the argument; philosophers and statisticians have been arguing about it ever since Carter proposed it.

Carter's "hard steps" model of our evolution on Earth is similarly probabilistic in nature. The sun is nearing the halfway point of its approximately 10-billion-year lifespan, and yet it's taken us — Homo sapiens — nearly all of that time to arrive on the scene. Carter could not see any reason why it would take so long for human-like life to evolve on Earth if complex life is common in the universe. This suggested to Carter that the development of human-like life must be difficult, passing through a series of evolutionary bottlenecks for which the chances of life succeeding are so remote that we would not typically expect those evolutionary transitions to occur in the lifetime of Earth. Life on our planet would therefore be a complete fluke, unlikely to be repeated elsewhere in the universe.

The hard steps idea has subsequently morphed into the concept of the "great filter," the idea that something in the history of all life inevitably brings that life to an end. Suggested great filters have included the origin of life in the first place, the evolution of technological life and the ability of said life to wipe itself out. The existence of the great filter would certainly help explain the apparent "great silence" in the universe that SETI (search for extraterrestrial intelligence) researchers have encountered, with no confirmed evidence of alien life in all the decades that we have been searching.

However, like the Doomsday argument, the "hard steps" model has its critics, and now adding to them are the authors of a new paper that highlights what they say is a fallacy in Carter's reasoning.

Carter specifically assumed that the age of the sun, and therefore the Earth, should have no bearing on how quickly complex life evolved. However, the new paper by Mills (a geomicrobiologist), along with Penn State University co-authors Jennifer Macalady (a professor of geosciences), Adam Frank and Jason Wright (both astrophysicists), points out that the age of the sun and therefore the Earth very much have something to do with it.

The team selected five of the more universally agreed-upon "hard steps:" the origin of life, the evolution of eukaryotes (organisms with cells made from a nucleus containing genetic information surrounded by a membrane), the oxygenation of Earth's atmosphere, the development of complex multicellular life and the arrival of Homo sapiens. They then looked at how geological and atmospheric changes to Earth might have affected when these supposedly hard steps occurred. If Earth were initially hostile to these supposed hard steps, it would naturally explain why they took so long to pass — because they had to wait for Earth to reach the point where they could be possible.

Take, for example, the oxygenation of Earth's atmosphere. For over two billion years after its formation, Earth's atmosphere was mostly carbon dioxide. It was only about 2.1 to 2.4 billion years ago that Earth's atmosphere began to fill with oxygen. This was thanks to the onset of photosynthesis, brought about by the evolution of microbes called cyanobacteria. In turn, the development of cyanobacteria relied on certain climactic and environmental conditions. In some models, the oceans of this era were hot, and the water would have had to cool below 70 degrees Celsius (158 degrees Fahrenheit) for cyanobacteria to evolve. In other models, conditions were milder and the development of cyanobacteria then depended upon the availability of freshwater and how much of Earth's landmass was above sea level. Either way, cyanobacteria's evolution and the onset of photosynthesis and the oxygenation of the atmosphere was delayed until these conditions were met; it couldn't have happened any sooner.

And even once cyanobacteria were ingesting carbon dioxide and exhaling oxygen via photosynthesis, it took time for oxygen levels to build up. Multicellular life requires a certain abundance of oxygen, with more complex life in general requiring more oxygen. The oxygen abundance in the atmosphere suitable for the evolution of Homo sapiens didn't occur until 400 million years ago — meaning that for 91% of Earth's history, there wasn't enough oxygen in the atmosphere to support human life.

In other words, Mills' team propose that these were not "hard steps" as Carter saw them, but that life simply had to wait until Earth could facilitate them — that Earth and life had to co-evolve together.

Related: Fermi Paradox: Where are the aliens?

Other variables that may have had an effect on how soon the different stages of life's evolution could occur include atmospheric ozone levels, nutrient availability, decreasing sea surface temperatures, decreasing ocean salinity, snowball Earth periods in which the planet completely iced over, and the development of plate tectonics.

"This is a significant shift in how we think about the history of life," said Macalady. "It suggests that the evolution of complex life may be less about luck and more about the interplay between life and its environment, opening up exciting new avenues of research in our quest to understand our origins and our place in the universe."

We know from geological evidence that life existed on Earth as early as 3.7 billion years ago, and possibly even earlier. The initial development of life on Earth is known as the "habitability boundary." As different windows of habitability subsequently opened up, life would have been able to evolve in bursts. And if this is the way it happens on Earth, it could be the way it happens on other worlds, too — and perhaps faster or more slowly, depending upon how the geology of those worlds develops.

There is a caveat, in that evolutionary biologists still do not understand how life originated on Earth. This moment of genesis is currently lost in the mists of time, and we cannot yet say whether it was a fluke one-off event or whether it was an easy step. One possibility is that life developed on multiple occasions on Earth, but all the other lineages went extinct, leaving only ourselves — the descendants of LUCA, the last universal common ancestor, from which all known life on Earth evolved — as the only ones left standing. This would give the illusion that life originated only once when it could have had several independent origins.

Other mysteries include how biological cells first evolved, and what caused the dramatic onset of complex life during the Cambrian explosion 540 million years ago.

It is still entirely possible that these were unique and rare events, but the new paper is not arguing that life is common in the universe, only that the concept of hard steps in evolution is not necessarily true and that the development of planetary environments has a big role to play, counter to Carter's original model.

Another caveat is that, so far, astronomers have not yet found another world like Earth, so geologists cannot yet say whether the way in which Earth's geology and atmosphere developed is typical or not. It could yet be that creating a habitable world is where the hard steps really lie.

Until we discover true extraterrestrial life, whether that be microbes on Mars or bonafide little green men, we will continue to grapple with the possibility that Earth and its life are unique. For now, it's a lonely universe out there.

The Mills et al paper was published on Feb. 14 in the journal Science Advances.

The chemistry of life as we know it wouldn't work in a place like the huge Saturn moon Titan, where it's so cold that ice behaves more like rock, or in the acidic clouds of Venus. But a different chemistry, which built all the requisite pieces out of different materials, might have a shot. Imagine cells that use methane, sulfuric acid, or even molten rock the way your cells use water.

According to a 2021 study by Massachusetts Institute of Technology (MIT) molecular biologist William Bains and his colleagues, it turns out that, if we're looking for life as we don't know it, the best solvent out there may be concentrated sulfuric acid — the stuff that's floating around in the clouds of Venus.

Sulfuric acid: Hazmat or solvent for life?

At the most basic level, life is just a series of chemical reactions. Those reactions need a medium in which to occur, which chemists call a solvent: something fluid enough that molecules can float around and mingle, and there needs to be a lot of it in one place. But not just any liquid will do; a solvent also needs to help break down and transport the chemicals that cells need to live — without also dissolving important molecules like lipids and amino acids.

Related: Alien life could thrive in Venus' acidic clouds, new study hints

Here on Earth, water fits the bill perfectly, but it may not be the only liquid in the universe capable of supporting the chemistry of life. In a new study, Bains and his colleagues rated several possible solvents based on how they interact with the chemical building blocks of life and how common they should be on rocky planets.

Candidates ranged from the liquid forms of methane and ethane, ammonia and carbon dioxide to even stranger possibilities like pitch and molten rock. The surprising champion is a chemical we Earthlings think of as painfully hostile to life: concentrated sulfuric acid.

"Even very complex organic chemistry is compatible with concentrated sulfuric acid," MIT astrobiologist Janusz Petkowski, a co-author of the new study, which was published in December in the journal Astrobiology, told Space.com.

A nod to the runners-up

Titan's frigid lakes of methane have been a hotspot for speculation about life as we don't know it ever since NASA's Cassini Saturn orbiter sent home the first photos of them in 2005. Methane and ethane are gases at the temperatures we find here on Earth; to condense into the liquid that fills the dark seas of Titan, they need temperatures around minus 250 degrees Fahrenheit (minus 157 Celsius). But in such extreme cold, atoms and molecules move sluggishly, so chemical reactions happen in slow motion — far too slowly for life to happen, according to Petkowski.

At the other end of the spectrum, molten rock is out because the tremendous heat required to keep rock liquid also breaks down nearly all organic molecules.

Some chemicals, like ammonia, have all the right properties to make good solvents for life's chemistry to happen in. But that may not matter, because the same processes that equip a rocky planet with ammonia are also likely to stock it with water, and when that happens, the two substances almost inevitably mix. That's an interesting prospect for life in its own right, because ammonia lowers the freezing point of water, which opens up a wider range of places where life could survive the cold.

"While ammonia may play a bigger role in an exoplanet biochemistry than it does on Earth," Bains and his colleagues wrote in their recent paper, "It is unlikely to be a solvent in its own right."

Life on an acid world

So, if astrobiologists ever do find alien life with a weird chemistry that uses some liquid other than water, it's not likely to be methane, ammonia, or molten rock — but somewhere out there, alien life just might have cells filled with pure sulfuric acid.

Based on physics models of how solar systems form, sulfuric acid should be fairly common on rocky planets like Venus, and it's definitely good at dissolving things. But surprisingly, some of the most important building blocks for life — things like amino acids and lipids — can float around and do chemistry in pure sulfuric acid just as easily as they can in water.

"Classically, [sulfuric acid] is not seen as a great solvent [for life]," Dirk Schulze-Makuch, an astrobiologist at the Technical University of Berlin who was not involved in the recent study, told Space.com. "However, Bains and co-authors showed that an amazingly large number and various types of organics are stable in concentrated sulfuric acid. That was quite surprising."

Petkowski participated in some recent experiments that found that some peptides (short chains of amino acids) were actually stable in concentrated sulfuric acid for months on end — so stable that eventually the researchers just got bored with the measurements, according to Petkowski. Earlier experiments found that 19 out of the 20 amino acids that form proteins in the human body don't dissolve in concentrated sulfuric acid. And a study that's still awaiting peer review found that not only can lipids (the molecules that make up our cell membranes) withstand concentrated sulfuric acid, they actually start to form tiny fluid-filled sacs that look a lot like vesicles, the precursors of membranes.

How does that happen? Strangely, the key is water. Sulfuric acid on Earth is usually found mixed with water, not in its pure form; it's really water with some acid in it. And in that mixture, sulfuric acid catalyzes chemical reactions between water and the bonds that hold peptides together. Take away either the water or the acid, and those reactions can't happen — so peptides are stable in either solvent, but not in a mixture of the two.

"Concentrated sulfuric acid is a very different substance from diluted acid," said Petkowski. "It is a common misconception that sulfuric acid destroys all organic chemistry. This is wrong. It is a very aggressive solvent, but it is very aggressive to specific parts in organic molecules, like sugars." (For all its mildness to amino acids and lipids, sulfuric acid will absolutely destroy sugars, which make up a lot of the scaffolding on which life is built.)

Somewhere in the universe, sulfuric acid lakes could be teeming with life forms whose basic chemistry is only a little different from ours.

Related: The search for alien life

What are alien cells made of?

Alien life forms that use sulfuric acid in place of water would probably look surprisingly similar to Earth life, with some subtle but important differences in their chemical makeup.

"We should understand sulfuric acid as an environment that is not so alien as we think it is," said Petkowski. (That doesn't mean you can safely swim in concentrated sulfuric acid; your cells did not evolve for that. Please do not test it.)

For example, life in a sulfuric acid sea would have to use something sturdier in place of sugars, which disintegrate very quickly in sulfuric acid. On Earth, sugars are how cells store energy, and they also make up parts of cell walls. Aliens on Venus would use some other type of molecule to do the same things without falling apart.

"You have to adapt your organic chemistry to the solvent," said Petkowski. "You have to choose the chemical LEGO building blocks properly, but you can arrive with functionally the same structures at the end."

Other differences might be more subtle. Concentrated sulfuric acid doesn't break down most of the amino acids our bodies use, but it does cause small changes in their "side chains," strings of atoms that stick out from the molecule like a tail. And just a single chemical bond makes the difference between a peptide that's stable in sulfuric acid and one that breaks down. So aliens on an acidic world could still have cells made of amino acids and proteins, but they might look just a tiny bit different than ours.

The membranes that surround cells — keeping the chemical mechanisms of life inside and everything else outside — may look strikingly familiar, though. Those vesicle-like globules that appeared when Petkowski and his colleagues put lipids into sulfuric acid actually formed in exactly the same way that vesicles form in water: a process called pearling. First, the lipids form tubes, and then those tubes break apart into little vesicles. Life on an acidic world might use a different set of lipids than the ones in our cell membranes, but the physics of membrane formation would look the same, if Petkowski and his colleagues are right.

Astrobiologists like Petkowski, Schulze-Makuch, and others still aren't exactly sure how all the pieces of life as we don't know it might come together. But, as Petkowski pointed out, they're also not sure how a few groups of molecules here on Earth made the leap from chemistry to life.

"We are as far away from figuring out [the] origin of life in water as we are in concentrated sulfuric acid," Petkowski said.

It seems like a somewhat reasonable assumption that if other civilizations are out there in the universe, eventually they will discover how to emit powerful radio broadcasts. Radio waves are capable of traversing great interstellar distances, so they make a great calling card. This is the foundational assumption for the search for extraterrestrial intelligence (SETI). Strange radio signals might be a sign of an artificial transmission from an alien species.

But our Milky Way galaxy is swimming in radio emissions of all sorts, from exploding stars to the vibrational hum of the galaxy's magnetic field. Plus, humanity has developed a particular fondness for radio transmissions, so any radio search for aliens must deal with enormous quantities of human-caused signals.

Previous SETI searches have scanned large areas of the sky and flagged anything interesting that popped up. Then, researchers have combed through the flagged results by hand, searching for signs of artificial transmission while ruling out potential causes of human-made interference.

Previous SETI searches have also come up totally empty — which isn't a big surprise, since this semimanual technique limits how much data any one research team can process.

Enter COSMIC, the Commensal Open-source Multi-mode Interferometric Cluster. COSMIC is a computer and software system that piggybacks on that of the Karl G. Jansky Very Large Array, the iconic radio array located in the desert of New Mexico.

COSMIC is designed to automate the process of SETI searches as much as possible. By combining fast processing and a series of restrictive filters, the system searches signal after signal, deciding if it's likely to be artificial and, if it is, determining if it matches the signature of a known terrestrial source.

In particular, COSMIC searches for radio signals that are very tightly focused, suggesting that they come from a very small source, like a planetary surface. Next, it looks for Doppler shifting of that radio signal. If the signal comes from a planet, the motion of the planet will either redshift or blueshift the signal, depending on whether the planet is moving away from or toward us when the signal was emitted. If the system finds a signal matching these properties, it is flagged and advanced to the next stage of filtering.

Related: How AI is helping us search the universe for alien technosignatures

Next, the astronomers behind COSMIC know the properties of terrestrial radio emission. This unwanted artificial emission follows particular statistical properties. If the flagged signal of interest matches those properties, the signal is rejected. Any remaining signals are then flagged for further review.

The COSMIC system is a part of the VLA Sky Survey, which completed a scan of roughly 82% of the Northern Hemisphere's sky. All told, the COSMIC system analyzed over 950,000 individual pointings of the telescope. Although the system initially flagged thousands of potentially interesting signals, none survived all of the filtering steps.

In other words, a deep radio search of a good chunk of the Northern Hemisphere found no artificial radio signals.

Although this is initially discouraging, this result still represents an important advance in our search for alien life. We can use this data to narrow down the probabilities of life appearing on any one planet, and we now have a valuable tool for collecting and processing data in future surveys, which might turn up something much more interesting.

However, this theory clashes with our current understanding of cosmic evolution and will be extremely difficult to prove.

Water is one of the most abundant compounds in the universe, according to NASA. Aside from Earth, astronomers have found water in several places throughout the solar system, including scattered above and below the surface of Mars, inside the ice caps of Mercury, surrounding the shells of comets and buried in underground oceans on several major moons. Outside our cosmic neighborhood, researchers have also detected water on distant exoplanets and within massive clouds of interstellar gas that permeate the Milky Way.

Until now, scientists assumed that all this water gradually built up over billions of years as hydrogen, the most abundant element in the universe, combined with oxygen that has been forged in the hearts of stars and expelled via supernovas. But in the new study, uploaded Jan. 9 to the preprint server arXiv, researchers simulated the explosive deaths of giant, short-lived early stars — which each had a mass equivalent to around 200 suns — and found that they could create the conditions needed for water to take shape.

The water from these stellar explosions would likely have formed at the hearts of dense clouds of hydrogen, oxygen and other elements left behind by stars. It may have had concentrations up to 30 times higher than the water seen floating in interstellar space within the Milky Way, the researchers wrote in the study, which has not been peer-reviewed yet.

Related: Could a supernova ever destroy Earth?

If correct, the new findings would have big implications for scientists' understanding of galaxy evolution and extraterrestrial life.

"Besides revealing that a primary ingredient for life was already in place in the universe between 100 million and 200 million years after the Big Bang, our simulations show that water was likely a key constituent of the first galaxies," the researchers wrote.

Early cosmic uncertainty

One of the biggest issues with the new study is that scientists have never directly observed one of the early stars that the researchers are modeling, known as population III stars. Instead, researchers have only indirectly observed a few of these stellar trailblazers by analyzing the stars that were birthed from their remains, so it's still not certain what they were really like.

If there was abundant water in the early universe, it would also suggest that the cosmos should have accumulated much more water than we currently see in our surroundings.

One explanation for this that has been posited by other scientists is that the universe underwent a drying-out period during which large quantities of water were lost, according to Universe Today. However, it is unclear what the cause of this event could have been.

"There is also the fact that while water formed early, ionization and other astrophysical processes may have broken up many of these molecules," Universe Today reported, meaning that the water from the first supernovas may have been short-lived.

Although water is a key ingredient for life on Earth, there is also no guarantee that its presence in the early universe would have made extraterrestrial life more likely.

Stars that lie between 150 to 300 light-years away appear in the mosaic as tiny dots of light, representing roughly 0.1% of the full sky that surrounds Europa Clipper. The four brightest stars visible in the image are Alchiba, Algorab, Gienah and Kraz from the Corvus constellation.

This image is associated with the spacecraft's star map, which helps determine where it points. With such a map, the Europa Clipper will be able to orient itself for the long trek to Jupiter's icy moon, Europa. As such, onboard are a pair of small cameras called star trackers, which capture the images for the ultimate star map mosaic.

"Without knowing the spacecraft's exact orientation, it would be impossible to precisely point science instruments at Europa to collect data, or to accurately point the antenna toward Earth for communication," Mana Salami, a Jet Propulsion Laboratory systems engineer who works in guidance and control for Europa Clipper, said in a 2022 mission update.

The star trackers — formally known as the stellar reference units — provide guidance by taking pictures of stars, and then comparing the pictures in a computer that contains a catalog of stars with known positions. This provides a frame of reference for Europa Clipper, so that it can adjust for the precise targeting needed to reach its destination, as well as transmit data back home to Earth.

One most ambitious spacecraft ever created, Europa Clipper is a solar-powered robotic orbiter tasked with a vital mission to find out if the distant moon in Jupiter's orbit could possibly support life. To this end, the spacecraft's three main science objectives are determining the thickness of Europa's icy outer layer and how it interacts with the ocean below; investigating Europa’s composition; and characterizing the moon’s geology.

On its way to Jupiter's orbit, Europa Clipper will visit Mars' vicinity in March for a gravity assist, before it heads Earthward, and then eventually on a path to visit Europa. According to NASA, the orbiter will travel at least 1.8 billion miles (2.9 billion kilometers) before it reaches the Jovian system in April 2030.

From claims of aliens crashing on Earth and UFOs being hidden on military bases, to Mars being abnormally large and the moon turning green, space tends to attract some outlandish or at least highly unproven claims that should be vetted carefully.

Here are some of the biggest space myths and conspiracy theories that just won't go away.

1. The Apollo moon landings were fake

Twelve NASA astronauts walked on the moon between 1969 and 1972, but in the decades since Apollo 11 astronauts first set foot on the moon, many theories have been put forward claiming that the whole Apollo program was staged. However, the Lunar Reconnaissance Orbiter has since released photos of the landing sites as they appear on the lunar surface many years later.

Some of the questions moon landing deniers ask are "Why are there no stars in the sky in the moonwalkers' photos? Why are the U.S. flags fluttering on the surface? Why do you see footprints in the pictures, but no marks from the lunar modules that landed there?"

It turns out those questions are easy to answer than you may think.

There are no stars in the sky for the same reason you don't see stars during the day on Earth, according to NASA: The bright glow of daylight on the surface washes them out.

U.S. flags planted into the lunar soil had metal rods sewn in them to appear as though they were moving, according to NASA. Without these wires, the flag would have hung straight down, making for a pretty lackluster photo prop.

And the lunar modules, though heavier, didn't put prominent marks in the surface in some places because their mass was more evenly distributed than the astronauts' weight was in their boots.

2. NASA is a lie

Some people actually believe NASA's whole function is not to explore space, but to generate space-related hoaxes. (The Apollo moon landing is a famous example that we'll explore in the next slide.) People who believe this conspiracy, sometimes flagged with the hashtag "#NASAhoax" on social media, will say that amazing space pictures of Mars, Pluto and even Earth are fake, computer-generated imagery (CGI).

NASA was formed in 1958 "to provide for research into problems of flight within and outside the Earth's atmosphere, and for other purposes," according to the National Aeronautics and Space Act of 1958, which then-president Dwight D. Eisenhower signed into law shortly after the start of the space race against the Soviet Union.

Since then, NASA has launched hundreds of satellites into orbit around Earth, the moon and several other worlds. In fact, NASA spacecraft have orbited, flown by or landed on every planet in the solar system. NASA also sends astronauts into orbit, where they conduct research at the International Space Station (ISS).

If you're not convinced, you are free to travel to Florida's Space Coast to watch a rocket launch for yourself. It's also quite easy to see the space station and other satellites with your own eyes with the help of a satellite tracker.

3. The Earth is flat

This myth is so popular that there is even a group named after it: the Flat Earth Society. Members of the organization argue that the horizon is always at eye level, which they say would not be possible if the Earth were round. They also say there is no full movie of the Earth rotating from space — which is not true, as NASA has published multiple videos taken from satellites, including a live video of Earth from the ISS, which orbits our planet 16 times per day.

One way of demonstrating to yourself that the Earth is round is to consider how orbits of satellites work. Satellites constantly "fall" around the Earth as they are pulled around by our planet's gravity; they just need to be traveling fast enough at a high enough altitude to not slam into the atmosphere. Or, you can look at the amazing pictures taken by astronauts at the ISS.

4. Planet Nine will kill us

In April 2016, the New York Post tweeted, "A newly discovered planet could destroy Earth as soon as this month." The newspaper was referring to Planet Nine, a theoretical planet at the edge of the solar system. An accompanying video also claimed that the new planet would be throwing all sorts of asteroids and comets at Earth, which would supposedly end up pummeling our planet.

Although the existence of a ninth planet has not been confirmed, astronomers are actively looking for one to help explain motions of some objects in the icy Kuiper Belt, a vast region of icy objects beyond Neptune. If the planet is actually found, the planet will pose no threat to us, according to the California Institute of Technology's Mike Brown (who is one of the original backers of the Planet Nine theory).

5. Alien research is happening at Area 51

The 1996 movie "Independence Day" is one of the main sources of the Area 51 hoax, which claims that aliens and their technology — recovered from crashed flying saucers — are being studied secretly at a classified military base about 80 miles (130 kilometers) northwest of Las Vegas in the Nevada desert. Some people in the area around the base claim that they have seen strange lights or objects flying in or out of this area.

While the testing and development conducted at Area 51 is classified, the U.S. government has acknowledged its existence (although the CIA officially calls it "Homey Airport" or "Groom Lake").

A part of Edwards Air Force Base, the area was a known location for high-technology airplane flights in the 1960s and 1970s. It first served as a proving ground for Lockheed U-2 and A-12 OXCART spy planes as early as 1955. UFO sightings reported in the area were indeed unidentified objects, but only because the planes were top-secret — not because they were flown by aliens.

6. There is a killer planet known as "Nibiru"

Conspiracy theorists say another dangerous planet is Nibiru, which was first mentioned in the 1976 book "The Twelfth Planet," by Zecharia Sitchin. In the book, Sitchin translated ancient Sumerian cuneiform and claimed that the text is proof of a planet beyond Neptune called Nibiru that orbits the sun every 3,600 years.

Years later, self-proclaimed psychic Nancy Lieder claimed to have communicated with extraterrestrials who said Nibiru would collide with Earth in 2003. When that didn't happen, the date was moved to 2012 (and linked, of course, with the 2012 doomsday predictions). Of course, the collision never occurred, the world didn't end in 2012 and no astronomer has ever found a planet on a collision course with Earth.

7. There is a face on Mars

In 1976, NASA's Viking 1 spacecraft took a picture of what appeared to be a face on Mars. Immediately, some people said there must have been aliens on the Red Planet that left that face behind as evidence of their existence. NASA, however, pointed out that the suspected face is really just a pile of rocks casting shadows that resemble face-like features.

NASA followed up with better-resolution pictures taken from the Mars Reconnaissance Orbiter and the Mars Global Surveyor in 1998 and 2001, respectively. These new images made it quite clear that the "face on Mars" is nothing more than a trick of light and shadows on a completely normal Martian mound.

8. The moon Iapetus is an alien Death Star

Iapetus is a moon of Saturn that looks somewhat like the infamous Death Star in the "Star Wars" franchise, with a large crater that resembles the fictional weapon's superlaser focus lens. The Death Star is a planet-killing machine that destroys entire worlds with its outrageously powerful laser. It was prominently featured in the 2016 movie "Rogue One: A Star Wars Story," as well as in 1977's "Star Wars: Episode IV - A New Hope."

A Daily Mail article published in May 2016 claimed Iapetus is an artificial object crafted by aliens. As "evidence," the article cited a photo taken by NASA's Cassini spacecraft in 2004. In the photo, there's a line around the moon's equator that resembles the equatorial trench around the Death Star.

But this line isn't nearly as interesting as the Death Star's trench, which houses the battle station's engines, thrusters and docking bays. That line is nothing more than a mountain ridge, and Iapetus is actually just made up of boring old rock and ice. Cassini has flown by the moon to take pictures several times without being blasted by deadly alien lasers.

Saturn's moon Mimas, with it's giant crater Herschel, also looks surprisingly like the Death Star.

9. Saturn's hexagon is alien technology

Saturn's hexagon was first spotted when NASA's Voyager spacecraft flew by the giant, ringed planet in 1980. The bizarre, six-sided structure on the round planet's north pole caused quite the stir, because straight lines and polygons are not so common in nature.

Immediately after the Voyager returned its first images of Saturn's strange feature, even stranger theories arose to explain it, including that it was somehow related to alien technology, or perhaps even was a gateway to hell. The hexagon is not artificial, but rather a weird-looking hurricane at Saturn's pole.

NASA has done several flybys of this region with the Cassini spacecraft, studying the haze particles and other features of the storm, to try to learn more about its unusual properties.

10. Mars is as big as the moon

Originating in 2003, the infamous Mars hoax asserts that Mars was closer to Earth than it had been in the 60,000 years prior, and that the planet will appear as large as the full moon. What started out as a misconstrued email turned into a recurring rumor that gets reshared every August and, naturally, has spread to social media as it became more popular.

Although Mars is indeed relatively close to Earth in a cosmic sense, it will never be as large as the full moon. It will appear as a red dot in the sky, just as the ancient astronomers saw it. If you'd like to see Mars magnified, take out a telescope or look at one of NASA's spectacular Mars pictures.

11. The moon will turn green

In spring 2016, there was a rumor that the moon would turn green because several planets had aligned and caused an eerie glow, according to EarthSky. This was supposed to happen on April 20 and again on May 29 for the first time since 1596, the rumor alleged.

The moon never actually turned green, although it can appear red during a lunar eclipse, when the moon passes through Earth's shadow. In the same way sunsets often appear red, sunlight is scattered as it passes through Earth's atmosphere, casting a reddish shadow on the moon's surface.

Skywatching columnist Joe Rao debunked this green-moon myth. He pointed out that a full moon actually took place on April 22, 2016, and speculated that the April 20 date of the "green moon" might have to do with "National Weed Day," popularly known as 4/20. Considering that the last green moon supposedly happened 420 years ago as well, this doesn't appear to be a coincidence.

12. Earth will go dark for two weeks

In July 2015, a website called "NewsWatch33" wrote an article claiming that Earth would have 15 days of complete darkness that year. The website, which is actually a fake news site, was borrowing from an older version of the tale that has been circulating for years, according to debunking website Snopes.

As we all know, Earth did not actually experience that much darkness that year. (The article claimed that the alleged darkness was partly due to a Jupiter-Venus conjunction, which actually took place more than 500 million miles apart.) Darkness occurs when the Earth rotates, causing the sun to "set" on the local horizon. Brief periods of darkness can also happen when the sun is totally obscured during total solar eclipses, which occur rarely in any particular spot on Earth. But even during an eclipse, Earth is never completely in the dark.

13. Zero-gravity day will make you weightless

If you ever wanted to leap into the sky and soar like Superman, this hoax is for you. In late 2014 and early 2015, a widely shared story claimed that on Jan. 4, 2015, everyone on Earth would experience weightlessness due to a rare alignment of the planets. A doctored image of a purported tweet from NASA's Twitter account that went around on social media fooled a lot of people into believing the hoax.

But, of course, nobody floated off the surface of Earth that day. Earth's gravity is too strong for people to become weightless. The only way to experience weightlessness without going to space is to ride aboard a plane that performs parabolas, with some including a few seconds of weightlessness. This is sometimes nicknamed the Vomit Comet.

14. Alien spacecraft caused a mysterious explosion

Back in 2004, an expedition of Russian researchers working in Siberia claimed to have discovered "an extraterrestrial device" close to where the mysterious Tunguska explosion occurred. Scientists still aren't sure exactly what it was that blew up in the sky over Siberia that day in 1908, but the leading theory is that it was a large meteorite or an asteroid, according to Live Science.

The Tunguska incident flattened hundreds of square miles of forest, and signs of the destruction were visible even decades afterward. At the time, news reports claimed that evidence of aliens was found at the site, but this claim was never substantiated. "The Russian team stupidly stated long before they went to Siberia that the main intention of their expedition was to find the remnants of an alien spaceship," Benny Peiser, a researcher at Liverpool John Moores University in the U.K., told Space.com. "And bingo! A week later, that's what they claim to have found."

15. UFO was caught "refueling" at the sun

NASA has a fleet of sun-gazing spacecraft that keep an eye on space weather, especially during solar eruptions. In 2012, telescopic images appeared to show something in the shadows. On YouTube, some viewers said this could be a UFO that was refueling by using the solar plasma.

However, NASA pointed out that the feature is actually something called a "prominence," which has cooler and denser plasma than the outer atmosphere of the sun, or the corona. Scientists are still trying to figure out how solar prominences develop, but they're pretty sure it has nothing to do with aliens.

16. There is a ______ on Mars!

With NASA's Opportunity and Curiosity rovers regularly taking pictures of the Martian surface, viewers have the chance to check out what they're doing in almost real time. NASA puts the raw images online for the public to see. But over the years, some weird shapes have cropped up. In 2008, for example, the Opportunity rover appeared to photograph a female figure. Other photos have shown things shaped like animals, spoons or other items.

You can imagine that, with all of the rocks available on Mars, some of them would happen to look like familiar objects. In fact, the human brain tends to perceive meaningful images in random patterns — a phenomenon known as pareidolia.

When evaluating the claims, consider that the Martian environment is extremely harsh to life as we know it; the surface is baked with radiation, the "air" is mostly carbon dioxide and there's not much atmospheric pressure.

17. I just saw a bright UFO!

It's a familiar trope for police stations and astronomy writers. From time to time, somebody will call (or write) in to say they just saw a UFO in the sky. While UFO is the term used for any flying object that an observer cannot identify, many people claim that they are alien spaceships. They spotted a bright light around sunset, or saw a light moving around in an unfamiliar way.

While every situation is different, one common explanation for "UFOs" is actually another extraterrestrial object: Venus. Venus can be extremely bright when it's at its closest, because it's relatively near Earth. The planet is also extremely reflective because the sun's light bounces off the clouds. So before calling to say you've spotted a UFO, check your sky charts!

18. NASA can travel faster than light

If you've seen the "Star Trek" clips that show the Enterprise spaceship warping into another sector, you might have wondered how fast NASA is making progress on being able to move at the speed of light. The EmDrive has created years of speculation, with some breathlessly saying NASA must be on the verge of breaking the famed barrier.

In reality, NASA is downplaying the reports. The engine in question is a prototype that is producing some interesting results, such as appearing to create thrust when there was no reason for this to happen – and thereby violating Newton's Third Law of Motion. That said, NASA has not yet verified the results from these tests, and the engine has not been widely discussed in peer-reviewed research.

19. We've launched balloons into space!

With the advent of high-resolution, miniature cameras, several people have decided to strap these cameras on to high-altitude balloons and take pictures from up high. They've caught glimpses of blackness and, at times, taken interesting tiny passengers along (such as 1000 Lego minifigures). So they must be in space, right?

There's no way a helium balloon can get into space, according to the California Institute of Technology, and simple physics explains why. When a balloon rises into the sky, the air inside will expand in response to the dropping atmospheric pressure and eventually pop. Even Felix Baumgartner's stunning high-altitude balloon jump in 2012 was not actually from space, but from the stratosphere, which extends to roughly 31 miles (50 kilometers) above the Earth's surface.

At that altitude the air is thin enough to see the blackness of space, but thick enough to support special high-altitude balloons. The boundary between Earth's atmosphere and outer space is about twice as high as the upper limits of the stratosphere.

20. There are canals on Mars

Author Percival Lowell became one of space's first popularizers when he wrote many books for the general public back in the late 1800s and early 1900s. In these books and other writings, he said there were canals on Mars built by an intelligent civilization, perhaps to move water into desert-stricken areas. He claimed to have seen the canals in his own telescope, and produced several sketches that are still available on the internet today.

There are no artificial canals on Mars. Several spacecraft have flown by the planet or orbited it, and not one has caught signs of aliens from orbit. What they have seen, however, are smaller channels that were created by nature – likely from water, ice or other processes that cause erosion.

21. A star is flinging comets at Earth

A long-standing theory known as Nemesis supposes that there is some sort of "death star" on the outer edge of the solar system, whose orbital motions perturb comets in an icy region of objects known as the Oort Cloud. According to the myth, the star's gravity throws these comets toward the inner solar system, and these comets collide with Earth and cause mass extinctions once every 27 million years.

However, a 2011 study concluded that this idea is unlikely, because the comet strikes in recorded history haven't happened with any regularity. The pattern that was recorded in the hoax is actually a statistical artifact, or the result of researchers trying to find patterns in nature where they do not exist, the study's authors found.

22. There's life on Venus

Back in the 1970s and 1980s, the Soviet Union sent several uncrewed missions to study Venus. Ten of these Venera probes landed on the surface of Venus and were able to transmit data and images for a few minutes before succumbing to the planet's extreme atmosphere. In 2012, the Russian news service RIA Novosti reported that Leonid Ksanfomaliti, a scientist who worked on the Venera missions, suggested that the photographs showed living objects moving around on the planet's surface. (RIA Novosti ceased operations in 2013.)

These alleged life-forms on Venus are just an example of "letting your mind see patterns in low-resolution data that simply aren't real," Jonathon Hill, a research technician who processes images taken during NASA's Mars missions, explained to Space.com's sister site, LiveScience, in 2012.

According to NASA, the objects that appeared to be moving were actually camera-lens covers that automatically popped off of the cameras after landing LiveScience reports. These half-circle objects were seen in images from Venera-13 and Venera-14, two identical spacecraft that landed about 590 miles (950 km) apart. Both had two identical cameras — one in the front and one in the back — so it makes sense that the covers would appear in different places. Another photograph that Ksanfomaliti said was a scorpion is actually a blur in the image.

23. An asteroid is about to crash into Earth

This recurring rumor claims that a threatening "doomsday" asteroid is about to slam into our planet. An example from 2015 had an asteroid purported to hit Earth in late September, when it would supposedly wreak devastation from its impact point near Puerto Rico. NASA quickly dismissed the reports — which turned out, as usual, to be false. But that's not to say that asteroids will never hit our planet.

NASA and a network of monitoring telescopes across the world are cataloging all known asteroids wider than 459 feet (140 meters) across in line with a 2005 congressional mandate. (Smaller asteroids, if found, are also cataloged.) Of the space rocks discovered so far, NASA has not found a single asteroid that has a high probability of hitting Earth in the foreseeable future.

24. Aliens landed in Roswell, New Mexico

On a ranch in Roswell, New Mexico, so the story goes, an alien spacecraft crashed in 1947. While the accounts of exactly what happen vary, the legend claims that a disc or some sort of spacecraft was found on a ranch, and that the government quickly covered up the evidence.

While rumors of aliens circulated, some people speculated that the crash was just a plain old weather balloon that might not have been recognized by the local community. The U.S. military acknowledged the "spacecraft" was actually a weather balloon sent aloft as part of Project Mogul, which involved flying microphones on high-altitude balloons to listen for sound waves generated by possible Soviet Union nuclear tests.

25. Climate change isn't real

Earth is on an abnormal warming trend. Arctic ice is melting, the sea level is rising and temperatures are going to extremes in many locations around the world. Why is this happening? Anti-climate-change conspirators have many explanations: solar activity, radiation, the Earth's (and sun's) movements around the Milky Way, among other theories.

While there are many components of climate change, the fact that humans have contributed to it is indisputable, according to NASA. Temperature graphs show that the climate has not warmed this much, this quickly in all of Earth's history (as seen in geological records), and that the increase correlates with increased industrialization.

Additional resources

For more myths about space, you can read this article by How It Works magazine. Additionally, you can watch this video by BBC Earth Lab.

Bibliography

"National Aeronautics and Space Act of 1958 (Unamended)". National Aeronautics and Space Administration. https://history.nasa.gov/spaceact.html

"Modern myths of Mars". Proc. SPIE 6309, Instruments, Methods, and Missions for Astrobiology IX, 63090C (14 September 2006). https://doi.org/10.1117/12.676304

That could soon change, thanks to a new NASA flagship telescope being designed to seek out strange new worlds that could support life as we know it. Called the Habitable Worlds Observatory, the telescope is so massive it may even need to ride a next-gen megarocket like SpaceX's Starship to reach space; it will also require new technological innovations to hunt for Earth's twin across the light-years. Yet, even with such hefty demands, this project was tapped as a top priority for NASA in the Decadal Survey on Astronomy and Astrophysics 2020 (Astro2020), an influential report that aims to set a roadmap for the astronomy community within the decade following its release.

"The question 'Are we alone?' is one of the most significant questions, not just in the history of science, but in the history of humanity, and we are at the precipice of actually having the tools and technologies that are required to tackle this question in a rigorous and scientific fashion," Giada Arney, the interim project scientist for the Habitable Worlds Observatory, told a crowd of scientists during a plenary talk here at the 245th American Astronomical Society meeting on Wednesday (Jan. 15). "We might learn the answer to this question within our lifetimes, and the answer to that question is a discovery, the implications of which would ripple through future millennia."

Arney, a planetary scientist based at NASA's Goddard Space Flight Center in Greenbelt, Maryland, is working with a vast team of scientists to develop the Habitable Worlds Observatory into a powerful tool for astrophysics research and exoplanet discovery. Last summer, NASA opened a new program office at Goddard for the space telescope and announced it has earned $17.5 million in funding to explore some of the key technologies needed to bring the instrument to fruition. Now, the team is gearing up for a major science conference in late July to outline the science the Habitable Worlds Observatory could do.

"We're very early in the design phase of HWO," Arney said, using NASA's shorthand for the observatory. "We're still iterating through a number of design concepts, so we don't know exactly how HWO is going to look when it launches."

One thing is for sure, though: It's going to be big.

Lee Feinberg, HWO's principal architect based at Goddard, said in a separate presentation that NASA is currently envisioning a massive space telescope nearly 20 feet (6 meters) wide, and suggested it could get as large as 26 feet (8 m). The Hubble Space Telescope, for comparison, has a 6.5-foot (2 m) aperture, he said.

Even the smallest version of HWO will need a huge rocket to haul it into space. Blue Origin's New Glenn rocket, which has a huge 23-foot (7 m) fairing, could fit the bill, Feinberg said.

"It would be really challenging to fit in that rocket from a mass perspective, but these are the kind of details that we're trying to understand," Feinberg said.

For larger versions of HWO, SpaceX's massive Starship — currently the world's tallest and most powerful rocket, with a nearly 30-foot (9 m) payload bay, is an option not just for launching the rocket, but also as a way to return to the observatory in space for periodic servicing, just as NASA space shuttle astronauts did with Hubble, according to early designs.

The space telescope will have four primary instruments, including a super-sensitive coronagraph that can detect Earth-size planets around distant stars. A prototype of its coronagraph should launch into orbit in 2026 on NASA's new Nancy Grace Roman Space Telescope. Current HWO designs call for the coronagraph, a high-resolution imager, an advanced spectroscope and a fourth instrument yet to be determined.

The current plan for HWO is to launch the observatory sometime between 2030 and 2040 to catalog at least 25 Earth-like exoplanet candidates for biosignatures, or signs that life that could be present on those worlds. The oxygen, methane and ozone of modern Earth are examples of possible biosignatures, Arney said.

If HWO successfully finds those signs of life, it would be a watershed moment for humanity's understanding of how common life might be in the universe. The reverse, however, is also possible. If HWO samples 25 exo-Earth candidates and comes up empty, that could be seen as the first "upper-limit" on the frequency of life beyond Earth, Arney said.

"HWO will either tell us we are not alone, if there are bio signatures that can be observed on an exo-Earth candidate orbiting a nearby star, or it will tell us for the very first time just how alone we are," she said. "Either answer would be profound, and either answer would change the way we see ourselves in relation to the rest of the universe."

How far can they get? Can they shoot 10 miles upward? 100 miles? 1,000 miles? Those aren't very far-fetched possibilities, considering how utterly teensy such particles can be. But, is there a limit? Well, maybe, but before hitting that limit, some scientists argue that the particles could get unfathomably far — like, all the way to another planet far. And, as if that weren't interesting enough, one crew is also thinking about what this ejecta can hold.

Earth ejecta, for instance, could hold Earth life.

"We're trying to figure out how much mass is reaching Venus from Earth, and how many cells can that mass carry," Emma Guinan, first author of a paper on the topic and a researcher at the School of Earth and Space Exploration at Arizona State University, told Space.com during the 2024 American Geophysical Union conference in Washington, D.C. "What if there was life, but it's transferred from Earth because there's already life here?"

Here's the theory

Guinan and her research team think it's possible that asteroids that impacted Earth over the last few billions of years may have periodically forced Earth material — holding things like plant cells and single-celled organisms — into space, and that if a tiny amount of those cells survived the harsh journey through space, they could've reached Venus. If true, those robust cells may still be living in Venus' atmosphere. Some could have even conglomerated together, speckling the world with the organics we have long assumed are confined to ours.

"Lucky for us, when cells are being transferred, they do tend to come together," she said. "So, there would be multiple cells being transferred at the same time. It wouldn't just be like one cell all by itself getting delivered to Venus."

The entire concept is called "panspermia," formally defined as the transfer of life from one part of the universe to another, and, surprisingly, it isn't really a wild new thing. It has been talked about for quite a while, and some scientists even believe that life on Earth may have arrived through panspermia, originating somewhere in deep space before being brought to our planet.

Yet, if you're wondering why we're fixating on Venus with this discussion — theoretically, as many publications would suggest, panspermia could happen across the solar system — it's because scientists discovered evidence of phosphine, a compound of phosphorus and hydrogen, in the amber world's atmosphere. Phosphine is considered an indicator for life (as we know it, of course).

A billion cells over a billion years

"We found there's roughly 1 billion cells per billion years being transferred to Venus," Guinan said of her team's calculations. This doesn't, however, mean that exactly one cell per year gets sent to Venus, because impactors that create the ejecta holding such cells aren't exactly regular occurrences. The calculation simply means that an average of a cell per year probably makes it from Earth to its evil planetary twin.

Plus, there is an important caveat: "We're not saying that all cells are viable. We're not even saying that they're surviving the transfer, or surviving in the atmosphere — but they are being transferred."

As Guinan points out, the area in Venus' atmosphere where such transferred life may exist is within a range from 28 to 37 miles (45 to 60 kilometers) above the planet's surface. This is a cloud layer, and she says it exhibits very similar temperature, atmospheric pressure, and other environmental factors we're experiencing right here on Earth's surface. However, because it's in the planet's clouds, it's pretty different from the conditions we live in. "It's not really super connected to life," she said, "so that's why everyone's kind of like, 'Okay, can these microbes survive in these conditions?'"

This brings us to the next steps in this saga — answering the questions that could give this theory some footing.

First of all, can these cells in ejecta particles survive the transfer from Earth to Venus? Space isn't for the weak; it's filled with radiation, micrometeorites, and who knows what else. But, okay, say some cells miraculously survived the journey. We'd need to know whether those cells managed to survive the atmosphere of Venus as well, which is famously hot, thick, and honestly hellish in many areas (recall the evil twin reference).

And then, those cells would need to successfully proliferate within the atmosphere of Venus.

Guinan says that proponents of the theory believe more infrared imaging and spectroscopy analysis of Venus' atmosphere could provide some answers to these major questions, and thinks a mission to Venus would prove invaluable in this case. NASA, for instance, is currently planning two missions to the planet — DaVinci and Veritas — both of which should be able to dissect new features about Venus' clouds. Depending on what they find, we may begin wondering about something peculiar.

Could our first detection of life beyond Earth simply be life from Earth?

"Most of the search for life, or life signatures, on other planets is actually proving that whatever we observe can be generated through means that do not require life," David Benoit, a senior lecturer in Molecular Physics and Astrochemistry at the University of Hull's E.A. Milne Centre for Astrophysics who was not involved in the study, told Space.com. "This study shows another pathway to produce molecular oxygen which was not previously always considered viable."

Before the massive rise in atmospheric oxygen (O2) on Earth during the Great Oxidation Event approximately 2.4 billion years ago — when cyanobacteria living in the oceans started producing oxygen through photosynthesis — our planet's primitive atmosphere was dominated by carbon dioxide (CO2) with only trace amounts of oxygen.

"Those O2 molecules were exclusively produced via abiotic [non-biological] processes," writes the team of researchers led by Shan Xi Tian and and Jie Hu at the University of Science and Technology of China.

Tian and Hu say they were fascinated with how this primitive atmospheric oxygen was formed, reporting a new mechanism through which that could've happened.

Others, meanwhile, propose the oxygen's formation through mechanisms like what's known as the "three-body recombination" reaction of two oxygen atoms or the dissociation of CO2 under ultraviolet light. It's also possible, some believe, that the substance could have come about through specific reactions with electrons. "However, we found a distinctly different pathway to produce O2 from molecular CO2," Tian told Space.com. "Namely, through the reaction of helium ions [He+] with CO2."

Most helium ions are produced when alpha particles in the solar wind interact with molecules in the upper atmosphere, creating charged particles known as ions that then react with CO2 that could then form O2. "This reaction should be observed in the upper atmosphere of Mars, because lots of He+ ions (due to solar winds) and CO2 exist there," explained Hu.

However, even though these reactions were confirmed to create various ions, such O+, O2+, and CO2+ in the Martian ionosphere, there is still no evidence to say O2 is formed this way.

To prove their theory, the scientists employed time-of-flight (TOF) mass spectrometry, a technique that determines the mass-to-charge ratio of gas-phase ions by measuring the time it takes for them to travel a known distance within an instrument called the spectrometer. This method relies on the principle that ions, accelerated by an electric field of known strength, acquire different speeds depending on their mass-to-charge ratios and, therefore, reach the detector at different times.

But Hu and Tian took this a step further, combining TOF with what're known as "crossed-beam apparatus" and "ion velocity maps" to try and elucidate any possible mechanisms that would yield molecular oxygen. In this setup, two beams of particles — CO2 and He+ — intersected under controlled conditions, allowing reactions to occur at the collision point.

The resulting products were ionized; their mass-to-charge ratios were determined based on the time it took for them to reach the detector. Simultaneously, ion velocity mapping recorded the trajectories and velocities of the ions, providing detailed information about their energies.

All in all, the team was able to reconstruct the reaction pathways and gain critical insights into the step-by-step processes leading to oxygen formation from these two starting materials.

"This is a useful finding which demonstrates that colliding helium at the sorts of energy we would observe in solar winds, can generate molecular oxygen when it hits carbon dioxide," said Benoit. "The efficiency of the process appears to be similar to that of colliding carbon dioxide with low-energy electrons, which was investigated a few years ago by the same research group."

Because life on Earth is closely tied to oxygen concentrations, scientists have long studied atmospheric oxygen as a potential marker of habitability on other worlds — especially given that most oxygen on Earth is produced by living organisms. However, this research demonstrates that oxygen can also form through abiotic processes, or processes that aren't rooted in living organisms. Thus, if similar mechanisms operate on other planets with CO2-rich atmospheres, oxygen could exist even in the absence of life.

This discovery, however, doesn't mean astronomers will hastily draw conclusions or that the search for life on exoplanets will be derailed by false positive biosignatures.

Benoit emphasized that cross-validation with astrochemical models and experimental observations would strengthen the findings. For instance, the simultaneous detection of carbon dioxide, helium and oxygen on an exoplanet could validate this pathway as a significant mechanism for molecular oxygen production.

"This new mechanism will likely be incorporated into future models used to predict the atmospheres of other planets," Benoit said, "and will help us better explain the quantities of oxygen we might find there."

The Mars methane mystery has befuddled scientists for years. Rovers on the surface have observed seasonal fluctuations of methane, but orbiting satellites have not found any significant trace of the molecule. This kind of variability is an intriguing, but unproven, hint that a particular kind of life might exist on Mars.

Broadly speaking, however, Mars appears to be uninhabitable. The surface temperatures are usually well below freezing, there's barely any atmosphere, and deadly cosmic and solar rays constantly bombard the planet. So, while ancient Mars once had oceans and warmer climates, we're unlikely to find any living creatures on or near the Martian surface.

Related: Alien life could lurk on Mars beneath protective ice, study suggests

But we can look to Earth to find potential habitats for Martian life. On our planet, life has expanded and diversified to fill every available niche, from the upper reaches of the atmosphere to miles below the surface. Life has also found many clever ways to extract energy from the environment. Although the most common method is photosynthesis — and the resulting food web from that base — the domain Archaea consists of single-celled creatures that find energy wherever they can get it.

This includes the methanogens, creatures that "eat" hydrogen and excrete methane as a waste product. These are prime candidates for potential surviving Martian life, given the evidence for the regular appearance and disappearance of methane on the Red Planet.

In a recent paper submitted to the journal Astrobiology, scientists scoured Earth for potential analogues to Martian environments, searching for methanogens thriving in conditions similar to those on Mars.

The researchers narrowed the list of potential habitat analogues to three categories. The first was microscopic fractures deep in Earth's crust, where the bedrock hosts tiny amounts of fluids — conditions that also might appear deep in the Martian crust. The second was freshwater lakes buried under glaciers or polar ice caps, which might exist under Mars' southern ice cap. And the last was extremely saline, oxygen-deprived deep-sea basins, which replicated the possible seasonal appearance of water on crater slopes on the Red Planet.

Scientists have already found methanogens in all of these environments on Earth, but that's not precise enough. In the new paper, the researchers mapped out the temperature ranges, salinity levels and pH values across sites scattered around the planet. Then, they narrowed down the species that thrived in conditions that resembled Martian conditions. Lastly, they surveyed the sites for the availability of molecular hydrogen, which is the primary food product of methanogens on Earth and potential life on Mars.

In particular, the researchers noted that the families Methanosarcinaceae and Methanomicrobiaceae were the most flexible, with member species living in a number of Mars-like conditions.

Next, the researchers examined available data about Mars itself. While information is scant, especially about subsurface conditions, there's enough data to put together a rough map of where liquid water might exist. Liquid water is essential for supporting all life, even the hardy methanogens. Given the circumstantial evidence for subglacial lakes and moist crater slopes, the researchers think the best chance for life is deep under the surface.

Specifically, Acidalia Planitia, a broad plain in the Martian northern hemisphere, has the best possible conditions. But the temperatures are only warm enough to support liquid water at a depth of 2.7 to 5.5 miles (4.3 to 8.8 kilometers). The researchers think the temperatures, salinity, pH and availability of hydrogen there have the best chances of matching conditions where methanogens thrive on Earth. So it's time to start digging.

There have been back-to-back open Congressional hearings and several classified gatherings in hush-hush, closed-door sensitive compartmented information facility (SCIF) settings. "Whistleblowers" toot tales of retrieved objects and super-secret reverse engineering efforts to look under the hood of recovered vessels. Even claims of non-human "biologics" being pulled out of the wreckage of crashed craft.

No single explanation addresses the majority of UAP reports, points out the All-domain Anomaly Resolution Office (AARO), the U.S. Government lead for diving in and deciphering the nature of now joined at the hip and lip lingo, UAP/UFOs. So what should happen in 2025 to move the UAP/UFO story forward? Are we at a dead-end? Conversely, is the coming year one of "full disclosure?"

Perhaps humanity is going to be on the receiving end of a shocking revelation that we are accompanied minors in a grown-up universe of intelligent civilizations?

Whatever the case, adult supervision seems advisable. On that pursuit, Space.com asked several leading UFO/UAP experts to look ahead into 2025.

Promising promises

A number of civilian institutions are making promising progress said Mark Rodeghier, president and scientific director of the J. Allen Hynek Center for UFO Studies, based in Chicago, Illinois.

What Rodeghier personally hopes to see in 2025 is continued progress with these groups, and others, new people entering the field with expertise and energy, and more development of the academic/professional UFO community.

"All of that will move the story forward, though at a sedate pace," Rodeghier said. To truly make a significant difference — barring some amazing case, or "disclosure" with a capital D, or a detection by SETI researchers of an alien signal — he would like to see:

• NASA take an active role and decide to fund proposals directly on the UAP subject
• Congress mandate funding via, for example, the National Science Foundation, to support research on UAP
• AARO to be more open, within understandable constraints of classification, to releasing their case investigations, and especially, of course, the case investigations for sightings which they cannot resolve.

"I'm not that hopeful, even given good intentions, that more Congressional hearings will be much help, without new whistleblowers with firsthand testimony," continued Rodeghier. "Otherwise, I want Congress to make certain that AARO has the resources required and to conduct thorough oversight of AARO's work," he said.

Hearings, legislation

Next year will see more congressional hearings, possibly additional legislation, and holding the DoD's AARO office publicly accountable, observes Jeff Gould who runs the UAP News Center, an informative website that finds and links to UFO daily news.

"Congress has clearly been deeply interested in the issue in the past three years. I anticipate that they will continue to pursue the UAP topic," said Gould. He expects more former government officials coming forward to speak on the topic.

Wild card ahead?

Gould said the scientific community will advance in two ways.

"There will be increased willingness by the larger scientific community to broach the topic," and anticipates more papers of greater depth going forward. This year, he said, academic papers included a civilian astronomer's guide to UAP research, the commissioning of an all-sky infrared camera array for detection of airborne objects, as well as detecting extraterrestrial life with astophotonics.

Additionally, there are research organizations focused on UAP that will continue to deliver relevant research, Gould said, including Harvard's Galileo Project, Stanford University's Sol Foundation that's a think tank undertaking cutting-edge inquiry into all aspects of UAP, as well as The SETI Institute.

"The wild card is the Trump administration," Gould said. "They seem to have a bias towards declassification. Will they declassify UAP related documents? We'll see," he concluded.

Conspiratorial-driven mythos

In 2025, science needs to get serious about studying UAP, "or we will be stuck at a dead end of the conspiratorial-driven mythos," said Alejandro Rojas, a consultant for Enigma Labs that labels itself as the "#1 destination for UFO sighting alerts."

The newly found credibility of the topic, said Rojas, "has highlighted a blind spot the Pentagon had toward detecting low-tech small craft flying within secured airspace on land and sea."

While concerning, that's a very terrestrial and human problem, Rojas added.

Government conspiracies

"Regarding the anomalous side of the issue, public interest is centered on unsubstantiated claims of government conspiracies regarding aliens and Roswell [New Mexico]. To some, UFO disclosure only means 'tell me what I already know, aliens are here and the government interacts with them.' Opportunists, many of them longtime proponents of alien conspiracies, tell the public what they want to hear sans evidence," said Rojas.

The outcome is that this creates a lot of distrust and foments a hostile attitude towards scientists and those trying to research the topic methodically, Rojas said.

"I think that we will never know what is truly going on until we make a space where we can publicly and transparently engage in and encourage hard data collection from sensor systems and careful scientific analysis of that data," Rojas advised.

Increased transparency and openness

Delving into the topic for 18 years, Robert Powell, executive board member of the Scientific Coalition for UAP Studies (SCU) explains that he's confident about one fact. "The UFO/UAP subject is not hindered by our calendar and will continue to move forward well past the year 2025," he said.

In the coming year, Powell spelled out SCU's agenda, promoting three areas:

• Federal and private investments in unclassified UAP science research by academia and the scientific community. Increased collaboration between scientists, researchers, and government agencies could foster a more rigorous and multidisciplinary approach to the study of UAP. This is an approach that we have never taken since the phenomenon began in 1942.
• Development of advanced UAP detection and sensor technologies. Significant sums of money are needed for the development and the deployment of networked sensor arrays.
• Increased transparency and openness in the study of UAP. We must move away from a military-based study of the phenomenon to a science-based study. The former is controlled by secrecy while the latter depends on openness and collaboration.

First contact

"It matters not whether one believes that UAP are controlled by an advanced intelligence," Powell said. "The more exoplanets we discover, the more we know that someday the time will come when we will make first contact with another intelligence."

Powell said there's need to start now to establish clear definitions of near-Earth technosignatures, communication protocols, and the responsible and ethical sharing of knowledge gained from such contact.

"Furthermore, we must consider who should represent humanity in such a momentous event," Powell observed. "Should it be a nation-state's military organization or an entity that speaks for all of humanity? This is a critical question with far-reaching implications for the future of our species," he said.

For one, the odd objects have sparked a visual public mayday and melee — one that might be mirroring elements of the ongoing unidentified anomalous phenomenon (UAP) issue, spurring talk of secretive saucer crashes by run-amok alien crewmembers with expired driver licenses.

Mischaracterization of what's seen. Public anxiety about what's not known. Government officials seemingly not clear on what's happening. Toss in Capitol Hill lawmakers demanding answers about what to do next. It's all enough to give you a case of the high- and low-altitude heebie-jeebies.

People don't usually look up

Jamey Jacob, executive director of the Oklahoma Aerospace Institute for Research and Education at Oklahoma State University in Stillwater, has some thoughts about what's likely going on.

Related: UFOs and UAP: History, sightings and mysteries

"This is a case of the general populace not being familiar with the density of air traffic in the national airspace, particularly on the Eastern Seaboard," Jacob told Space.com. "Most people today generally don't spend much time looking up at the night sky, and when you do, you finally start to see what's around you."

Jacob said that, while the possibility of drone threats is something that we should be concerned about — particularly since we're largely unprepared to deal with it — the present scenario appears to be mostly misidentification of piloted aircraft.

The drones that have been sighted, Jacob added, look to be generally operating under the U.S. Federal Aviation Administration's night authorization for drone pilots.

"Nefarious operations would as a rule of thumb not fly with navigation lights so [as] to be harder to track," said Jacob. "The misidentification of commercial airliners and private aircraft as drones are predominantly due to the difficulty of determining size and distance of a vehicle without a reference scale. Research that we have done on estimating size and location of both drones and manned aircraft back this up."

Does the government know more?

Others have different ideas, however. For example, the drone sightings are real and they are government- and/or industry-operated drones, said Robert Powell, an executive board member of the Scientific Coalition for UAP Studies in Austin.

"There are too many, and they are too large for them to be civilian," Powell told Space.com. "I don't think any adversary of the United States would dare try to fly drones into our territory at this level, and if they did, I would think we would respond."

Powell added that that he feels confident that government officials know much more about the drones than they are telling the public.

"This of course leads to the same type of problems as with the UAP issue. Anxiety kicks in and people see drones everywhere they look," said Powell.

Moreover, the media is not capable of distinguishing between reports of drones versus reports of normal aircraft, nor are they adept at asking the right questions of government officials, Powell said.

Kernel of truth

"Conspiracy theories start to grow because the government withholds information and makes nonsensical statements, such as 'We don't know where the drones come from or what they are, but we know they pose no risk,'" Powell said.

Some members of the public are indeed seeing drones, Powell said. "Amazingly, the same debunkers that argue against UAP are arguing against drones. They cite examples of misidentification, which of course exists."

Bottom line from Powell: "There is a kernel of truth in these drone reports, and I think the government knows the truth. I hope people will understand that as long as the government withholds information that this is the type of mess that unfolds."

Standard practice

"Many of these fly like human-made drones and others appear to be airplanes or helicopters," said Harvard astrophysicist Avi Loeb.

"It is standard practice for the U.S. military to notify law enforcement authorities of any plans to fly drones over residential areas," he told Space.com. "Therefore, unidentified drones must have originated from civilians or an adversarial nation."

Loeb is a co-founder of the Galileo Project initiative. Its goal is to bring the search for extraterrestrial technological signatures from accidental or anecdotal observations and legends to the mainstream of transparent, validated and systematic scientific research.

Inappropriate smoke screen?

As for drones from adversarial nations, Loeb said that possibility should come as no surprise, since a Chinese spy balloon was spotted back in early 2023 flying at a high altitude across the United States.

Even though the balloon was nearly 150 feet (45 meters) in diameter, Loeb recalled, it took a while for the U.S. Air Force to shoot it down off the coast of South Carolina.

Drones are used routinely in the current conflict in Ukraine, which began with the Russian invasion in February 2022. And drone technology has advanced considerably in recent years, especially in China, Loeb said.

"The primary question that needs to be clarified is whether these flying objects are used for espionage or pose any other national security threat," Loeb said. "Alluding to an extraterrestrial origin is an inappropriate smoke screen to hide the incompetence of the U.S. intelligence agencies."

The golden child in Saturn's system is named Enceladus, and it's so special because scientists believe it to be a prime location to search for life beyond Earth. That belief stems from several discoveries made over the years, most obviously the fact that Enceladus seems to have a subsurface ocean that may host molecules known to help produce life as we know it. Better yet, it also appears to have giant plumes of water ice deposits (think icy geysers shooting into space) connected to that ocean, which means spacecraft orbiting the world could theoretically catch evidence of those molecules if they're actually there.

Thus, when studying Enceladus, every detail really matters — which brings us to a new, very strange detail that scientists have their eye on: A weird, disappearing dark spot on this ice-capped moon. No one quite knows what it is yet, but it may tell us something about those plumes that could hold the precious building blocks of life we seek.

This dark spot was one of the intriguing topics of discussion during the 2024 American Geophysical Union meeting in Washington, D.C. — where scientists congregated to search for the final pieces in cosmic puzzles they've been working on all year.

Awe filled the room as Cynthia B. Phillips, a planetary geologist at NASA's Jet Propulsion Laboratory who presented the research, went into tremendous detail about how she and her team originally identified the dark spot. It was thanks to her crewmember Leah Sacks, who helped pore through a bulk of data about Enceladus, collected by NASA's Voyager and Cassini missions. The goal of the analysis was to compare images of the same region taken by these spacecraft in order to identify any changes on the moon's surface.

Possible changes could reveal awesome information about geologic activity on the world, but we'll get to that shortly; first let's dive into the mysteries of the dark spot.

"After staring at dozens and dozens of image pairs — she found something interesting," Phillips said during the conference. "It's a little dark spot; it's about a kilometer across. She spotted it in an image from 2009 and looked again in 2012 and it seemed to be gone."

The dark spot was slowly fading away and getting smaller as the years progressed, and it never became more pronounced again. How weird, and especially so because Enceladus has what's called a high "albedo." That basically means the world is really bright — it's therefore unexpected to find a dark spot on it at all, let alone one that's fading away. But before getting too excited, the scientists made sure to second guess themselves as much as possible to rule out the obvious caveats.

"First our question was," Phillips said, "'well, is it just that in some of these low resolution images, we're not seeing it, but it's really there?'" In short, the answer was a simple "no, probably not." For example, a direct comparison of a 2010 image and a 2011 image shows the dark spot smaller in the 2011 image, even though the 2011 image had a higher resolution.

The next question was: Is this a shadow of some sort? Well, nope. Doesn't look like it.

The team pulled out some images with lighting coming from different directions, and the location of the spot seemed consistent. The researchers even found a sequence of images with the dark spot where the light's angle of incidence (aka, the angle at which light strikes a surface) gets higher and higher. If the spot were a shadow, you'd expect it to become more prominent with a higher incidence angle. This wasn't the case — it still became less distinct as time went on. "We don't think it's topography; we don't think it's just a shadow," Phillips told Space.com.

And it didn't end here — the team also looked at images taken in UV light and color (the latter of which interestingly suggested that the dark spot is a reddish brown, unlike the usual blueish darker areas on other sections of the moon). None of this suggested an easy explanation for the feature.

So, what is it?

"I think the more likely [case] is that it is some kind of a crater," Phillips told Space.com. "And the reason why it's dark is maybe it's a chunk of some kind of dark material that landed on the surface, and you're either seeing some of that impactor left behind, and that's why it has that weird color, or you're seeing that when it impacted, it exposed some kind of bedrock of ice that was a different color."

But for almost every likely and mundane scenario in space research, there tends to exist a rare and exciting one serving as a counterpoint.

"The really cool explanation would be if it was actually coming up from underneath, somehow; if that reddish color was actually a sign of the interior composition of Enceladus," she said. "That's unlikely, but that'd be really interesting."

Still, although we don't know what the dark spot is, Phillips points out that there is indeed something pretty major we can derive from its presence: "'What is it?' I don't know the answer to that — but what I can say is: 'What can we use it for?'"

Remember the plumes

In a nutshell, the researchers think the dark spot appeared to be fading progressively because deposits from those icy Enceladus plumes might have covered it up. "We know the whole surface is covered by plume deposits — like little layers of ice building up over time," Phillips said.

Alas, in theory, this makes a lot of sense. But when you really think about it, there are some outstanding issues here.

For example, the team saw the dark spot fading over just a few years — this would imply that just a few years is long enough for ice plume deposits to create a sheet of ice thick enough to cover such a prominent spot. After all, it's visible from space! Yet, according to various calculations of the dark spot and models of the moon's plumes, Phillips says it should take something like 100 years to create a layer thick enough to cover this kind of spot.

"What this could mean, though, is that the plume deposition model, at least in this location, is an underestimate," she said. "One thing we haven't taken into account, though, is deposition from collisions with E ring particles."

E ring particles refer to the super small water ice particles in Saturn's rings. Potentially, the team reasons, some of those particles could be helping build the sheet covering the dark spot. But the story of this spot's origin and evolution, at this point, is mirrored by the abrupt ending of our story of its discovery.

There are simply too many unanswered questions.

"What would the deposition rate needed to cover the black spot in this time frame indicate about deposition rates? Is the E ring contributing to cover that spot? Is there maybe another mechanism?" Phillips pondered.

"And, you know, what is the black spot?"

This plan was prepared for the NASA Science Mission Directorate's Mars Exploration Program (MEP).

The report is titled "Expanding the Horizons of Mars Science: A Plan for a Sustainable Science Program at Mars — Mars Exploration Program 2024-2044."

Core questions

Highlighted in the document are several “paradigm shift” prospects to further address several core questions, which include:

How has the habitability of Mars evolved over the history of the planet?

Did life ever arise on Mars, and if so, does it exist today?

Related: Life on Mars: Exploration & evidence

The document also looks at lower-cost Mars missions. Commercial services, the human exploration of the Red Planet and international Mars ambitions are also flagged as paradigm shifts.

"NASA is no longer one of the few with focused Mars exploration ambitions," observes the report.

New, different model

"To remain a vanguard in Mars exploration, MEP must embrace a new, different model: the ability to send more — and more frequent — missions to Mars in an affordable and achievable manner, and to do so while cultivating a diversity of talent and engaging the public in opportunities to explore Mars,” the report points out.

The report defines a "lower-cost mission” as approximately $100 million to $300 million, exclusive of the launch vehicle and mission operations.

A “medium-class strategic mission" is pegged at between approximately $1 billion and $2 billion, exclusive of the launch vehicle and mission operations.

Partnerships

As for tapping into commercial services, the report states that exploring Mars together "through new partnership models with the international, commercial and academic communities is essential."

This type of paradigm shift would mimic other innovative public-private partnership solutions, such as NASA’s Commercial Orbital Transportation Services (COTS) and Commercial Lunar Payload Services (CLPS) endeavors.

Life on Mars

The search for life on Mars remains a significant undertaking, according to the new report.

“Any potential oasis for present life or preservation of ancient life are likely located in terrains that have historically been more challenging to access," the document states. "Some of the most fascinating landscapes on Mars, for example, are found in the southern hemisphere, where the mean surface elevation has prevented robotic spacecraft from landing by traditional means.”

At the same time, there are other locales providing conditions potentially conducive to life, such as the subsurface (including caves, subsurface ice deposits and volcanic environments), "where suitable chemistry and environmental conditions may have allowed life to gain a foothold," the report adds.

However, given the prospect of boots on Mars, NASA’s Mars Exploration Program "has a small window of opportunity to seek life in a pristine Martian environment, as human exploration may be possible as early as the late 2030s, following successes at the moon."

Challenge conventional thinking

Eric Ianson, director of the NASA Mars Exploration Program, states in the report that there’s a need to "challenge conventional thinking and look to new and creative solutions for the exploration of Mars."

This can include “seeking lower-cost science investigations, strengthening our infrastructure around Mars, seeking new enabling technologies and creating an environment that broadens participation in Mars exploration,” Ianson states.

You can read the new report here.

We have only one example of biology forming in the universe – life on Earth. But what if life can form in other ways? How do you look for alien life when you don’t know what alien life might look like?

These questions are preoccupying astrobiologists, who are scientists who look for life beyond Earth. Astrobiologists have attempted to come up with universal rules that govern the emergence of complex physical and biological systems both on Earth and beyond.

I’m an astronomer who has written extensively about astrobiology. Through my research, I’ve learned that the most abundant form of extraterrestrial life is likely to be microbial, since single cells can form more readily than large organisms. But just in case there’s advanced alien life out there, I’m on the international advisory council for the group designing messages to send to those civilizations.

Detecting life beyond Earth

Since the first discovery of an exoplanet in 1995, over 5,000 exoplanets, or planets orbiting other stars, have been found.

Many of these exoplanets are small and rocky, like Earth, and in the habitable zones of their stars. The habitable zone is the range of distances between the surface of a planet and the star it orbits that would allow the planet to have liquid water, and thus support life as we on Earth know it.

The sample of exoplanets detected so far projects 300 million potential biological experiments in our galaxy – or 300 million places, including exoplanets and other bodies such as moons, with suitable conditions for biology to arise.

The uncertainty for researchers starts with the definition of life. It feels like defining life should be easy, since we know life when we see it, whether it’s a flying bird or a microbe moving in a drop of water. But scientists don’t agree on a definition, and some think a comprehensive definition might not be possible.

NASA defines life as a “self-sustaining chemical reaction capable of Darwinian evolution.” That means organisms with a complex chemical system that evolve by adapting to their environment. Darwinian evolution says that the survival of an organism depends on its fitness in its environment.

The evolution of life on Earth has progressed over billions of years from single-celled organisms to large animals and other species, including humans.

Exoplanets are remote and hundreds of millions of times fainter than their parent stars, so studying them is challenging. Astronomers can inspect the atmospheres and surfaces of Earth-like exoplanets using a method called spectroscopy to look for chemical signatures of life.

Spectroscopy might detect signatures of oxygen in a planet’s atmosphere, which microbes called blue-green algae created by photosynthesis on Earth several billion years ago, or chlorophyll signatures, which indicate plant life.

NASA’s definition of life leads to some important but unanswered questions. Is Darwinian evolution universal? What chemical reactions can lead to biology off Earth?

Evolution and complexity

All life on Earth, from a fungal spore to a blue whale, evolved from a microbial last common ancestor about 4 billion years ago.

The same chemical processes are seen in all living organisms on Earth, and those processes might be universal. They also may be radically different elsewhere.

In October 2024, a diverse group of scientists gathered to think outside the box on evolution. They wanted to step back and explore what sort of processes created order in the universe – biological or not – to figure out how to study the emergence of life totally unlike life on Earth.

Two researchers present argued that complex systems of chemicals or minerals, when in environments that allow some configurations to persist better than others, evolve to store larger amounts of information. As time goes by, the system will grow more diverse and complex, gaining the functions needed for survival, through a kind of natural selection.

They speculated that there might be a law to describe the evolution of a wide variety of physical systems. Biological evolution through natural selection would be just one example of this broader law.

In biology, information refers to the instructions stored in the sequence of nucleotides on a DNA molecule, which collectively make up an organism’s genome and dictate what the organism looks like and how it functions.

If you define complexity in terms of information theory, natural selection will cause a genome to grow more complex as it stores more information about its environment.

Complexity might be useful in measuring the boundary between life and nonlife.

However, it’s wrong to conclude that animals are more complex than microbes. Biological information increases with genome size, but evolutionary information density drops. Evolutionary information density is the fraction of functional genes within the genome, or the fraction of the total genetic material that expresses fitness for the environment.

Organisms that people think of as primitive, such as bacteria, have genomes with high information density and so appear better designed than the genomes of plants or animals.

A universal theory of life is still elusive. Such a theory would include the concepts of complexity and information storage, but it would not be tied to DNA or the particular kinds of cells we find in terrestrial biology.

Implications for the search for extraterrestrial life

Researchers have explored alternatives to terrestrial biochemistry. All known living organisms, from bacteria to humans, contain water, and it is a solvent that is essential for life on Earth. A solvent is a liquid medium that facilitates chemical reactions from which life could emerge. But life could potentially emerge from other solvents, too.

Astrobiologists Willam Bains and Sara Seager have explored thousands of molecules that might be associated with life. Plausible solvents include sulfuric acid, ammonia, liquid carbon dioxide and even liquid sulfur.

Alien life might not be based on carbon, which forms the backbone of all life’s essential molecules – at least here on Earth. It might not even need a planet to survive.

Advanced forms of life on alien planets could be so strange that they’re unrecognizable. As astrobiologists try to detect life off Earth, they’ll need to be creative.

One strategy is to measure mineral signatures on the rocky surfaces of exoplanets, since mineral diversity tracks terrestrial biological evolution. As life evolved on Earth, it used and created minerals for exoskeletons and habitats. The hundred minerals present when life first formed have grown to about 5,000 today.

For example, zircons are simple silicate crystals that date back to the time before life started. A zircon found in Australia is the oldest known piece of Earth’s crust. But other minerals, such as apatite, a complex calcium phosphate mineral, are created by biology. Apatite is a primary ingredient in bones, teeth and fish scales.

Another strategy to finding life unlike that on Earth is to detect evidence of a civilization, such as artificial lights, or the industrial pollutant nitrogen dioxide in the atmosphere. These are examples of tracers of intelligent life called technosignatures.

It’s unclear how and when a first detection of life beyond Earth will happen. It might be within the solar system, or by sniffing exoplanet atmospheres, or by detecting artificial radio signals from a distant civilization.

The search is a twisting road, not a straightforward path. And that’s for life as we know it – for life as we don’t know it, all bets are off.

This article was originally published on The Conversation. Read the original article. Follow all of the Expert Voices issues and debates — and become part of the discussion — on Facebook, Twitter and Google +. The views expressed are those of the author and do not necessarily reflect the views of the publisher. This version of the article was originally published on Space.com.

NASA's Perseverance rover has finished an epic climb on Mars.

The Perseverance rover crested the rim of the Red Planet's Jezero Crater this week, wrapping up a 3.5-month-long trek during which it gained about 1,640 vertical feet (500 meters) and tackled 20% slopes with slippery, shifting footing.

"During the Jezero Crater rim climb, our rover drivers have done an amazing job negotiating some of the toughest terrain we’ve encountered since landing," Steven Lee, deputy project manager for Perseverance at NASA’s Jet Propulsion Laboratory (JPL) in Southern California, said in a statement on Thursday (Dec. 12).

"They developed innovative approaches to overcome these challenges — even tried driving backward to see if it would help — and the rover has come through it all like a champ," Lee added. "Perseverance is 'go' for everything the science team wants to throw at it during this next science campaign."

Related: NASA's Perseverance rover begins ambitious ascent up a Mars crater rim

Perseverance landed on the floor of the 28-mile-wide (45 kilometers) Jezero in February, on a mission to hunt for signs of past life on Mars and gather samples for future return to Earth.

The six-wheeled Mars rover has done this work over the course of four different science campaigns. As Lee noted, Perseverance made the rim climb to set up a new campaign — one the team is calling "Northern Rim."

"The Northern Rim campaign brings us completely new scientific riches as Perseverance roves into fundamentally new geology,” Ken Farley, project scientist for Perseverance at the California Institute of Technology in Pasadena, said in the same statement.

"It marks our transition from rocks that partially filled Jezero Crater when it was formed by a massive impact about 3.9 billion years ago to rocks from deep down inside Mars that were thrown upward to form the crater rim after impact," he added. "These rocks represent pieces of early Martian crust and are among the oldest rocks found anywhere in the solar system. Investigating them could help us understand what Mars — and our own planet — may have looked like in the beginning."

The new science campaign will be a lengthy and involved one; in the next year, Perseverance is expected to visit up to four different geological sites and cover about 4 miles (6.4 km) of Red Planet ground, mission team members said.

Perseverance reached the top of Jezero's rim at a spot the mission team calls Lookout Hill. The rover has already left that site and is rolling toward Witch Hazel Hill, an interesting outcrop about 1,500 feet (450 m) away.

"The campaign starts off with a bang, because Witch Hazel Hill represents over 330 feet [100 m] of layered outcrop, where each layer is like a page in the book of Martian history," Candice Bedford, a Perseverance scientist from Purdue University in Indiana, said in the same statement. "As we drive down the hill, we will be going back in time, investigating the ancient environments of Mars recorded in the crater rim."

After that, the rover will head toward Lac de Charmes, which lies about 2 miles (3.2 kilometers) south.

"Lac de Charmes intrigues the science team because, being located on the plains beyond the rim, it is less likely to have been significantly affected by the formation of Jezero Crater," NASA officials wrote in the same statement.

This is the result of a recent study that simulated exposing important building blocks of life called "lipids" to cosmic rays pummeling the surface of Mars. And, in short, the exposed material appeared to break down very quickly under the bombardment of radiation from space — and even faster when there was salt mixed in with the sediment, which is the case in many of the places we consider the most likely ancient habitats on Mars.

"We go for salt-rich environments, but they could be one of the most damaging under radiation," Georgetown University astrobiologist Anais Roussel told Space.com.

Erasing evidence of past life

"This is a big limitation we have in astrobiology, and the more we know, the better," says Roussel.

Roussel and her colleagues' work suggests that's a good reason to worry — especially in places on Mars that most likely stayed habitable as the planet became cooler and drier around 4 billion years ago.

In particular, the researchers focused on hopanes and steranes, the fossil forms of chemicals called hopanols and sterols. Hopanols are important parts of the cell membranes of bacteria, while sterols are part of the cell membranes of eukaryotes (organisms whose cells have nuclei; humans are an example)). Here on Earth, these two lipids represent some of the most resilient chemical traces of life; under the right conditions, they can survive in rocks or soil for billions of years. Plus, living cells are the only known source of these chemicals, so if they turn up, it's most likely clear evidence of life with chemistry similar to life on Earth.

Here on Earth, however, most rocks and soil aren't getting constantly pummeled by cosmic rays, thanks to the protection of our atmosphere and magnetic field. That's not the case on Mars. It lost those shields around 4 billion years ago. As such, when Roussel and her colleagues bombarded her samples of lipids with gamma rays to simulate the cosmic ray exposure on Mars, about half the lipids in her sample decayed into unrecognizable jumbles of smaller molecules, within the equivalent of about 3 million years of exposure on the Martian surface.

For context, some of the rock outcroppings at Gale Crater, home of the Curiosity Rover, have been exposed to cosmic rays on the Martian surface for about 80 million years.

"Three million years is a really, really short amount of time to get rid of such good diagnostic biosignatures," says Roussel.

The team’s lipid samples degraded about twice as fast as another important chemical that previous studies tested in similar experiments: amino acids, the chemicals that make up proteins, which are the literal building blocks of life. Roussel suggests that could be because lipids are much larger molecules, and their shapes are very different from amino acids, which means they’ve got more surface area available to be hit by incoming radiation.

And, again, radiation exposure isn't much of an issue on Earth — but on Mars, it could be a big one.

"We need to really keep all of these parameters in mind when we go to Mars, and try to avoid defining only one perfect place, one perfect biosignature, or one perfect target," says Roussel.

And then there's the salt problem

Most of the places astrobiologists consider the most likely to hold evidence of ancient Martian life are simply very salty.

As Mars's atmosphere grew thinner and its surface grew colder, fresh water either froze in the cold or boiled away under the low air pressure (depending on location). Briny streams and lakes would have been some of the last bodies of liquid to remain because salt water needs a colder temperature to freeze; salt also makes water a little harder to boil, so as the air pressure dropped, salt content should have kept the water from vanishing in a puff of vapor.

When it comes to preserving the chemical traces of whatever once lived in those briny ponds, though, salt does more harm than good.

"We don't know right now what specifically in the salt structure itself can create something that would further degrade organics," says Roussel. That's a question scientists are still working to answer. Radiation might cause chloride or sodium in the salts to form chemicals that react with organic molecules (like lipids), breaking them down into smaller pieces. On the other hand, if there's even a microscopic bit of leftover water still clinging to the salts, it could produce chemicals called oxidants, which also break down organic molecules very quickly.

Hope springs eternal, even if the springs are briny

The findings sound discouraging, but Roussel says they've actually made her more optimistic than ever about the prospect of life on Mars.

"Maybe if we didn't find anything conclusive so far, it doesn't mean that there was never life on Mars, but that we're just looking at the wrong place or that we need to go deeper."

In 2029, the European Space Agency's Rosalind Franklin Rover will have a chance to do exactly that. NASA's Curiosity and Perseverance rovers can only drill about 5 centimeters (about 2 inches) into the ground — that's not deep enough to reach rocks or sediment protected from cosmic rays. But Rosalind Franklin's drill will reach about 2 meters (78 inches), which is deep enough to avoid most, but not all, radiation exposure.

"My dream would be to see a mission going to a Martian cave or to a Martian lava tube, because one of those caves could be completely pristine from radiation," says Roussel. "That would be extremely challenging from an engineering point of view, but I think if you could go, this raises hope."

The study was published on Nov. 13 in the journal Astrobiology.

Even when you account for every technological hurdle — limits in rocket technology, speed and life spans, as well as disease, warfare and anything else that could slow progress — the argument stays the same. Our galaxy is over 13 billion years old, which is more than enough time for spacefaring civilizations to spread throughout the Milky Way.

Indeed, we should see advanced civilizations everywhere — Dyson spheres, stellar engineering, artifacts littered across the solar system. But we don't. So where is everybody? Hence the paradox: Something in this line of reasoning has to give. We've gotten one, if not many or all, of these statements wrong. Which one?

first detailed in 1996 by economist Robin Hanson. The most distilled essence of the Great Filter argument is simple: Very few, if any, civilizations in the universe make it to the advanced spacefaring stage.

That's it. Fermi's paradox is broken in its assumption that intelligent spacefaring civilizations are common.

Considering that humanity is on the cusp of achieving regular spacefaring status, the Great Filter might seem a little ominous. But it doesn't have to be. The issue is that we don't know exactly when or where the filter actually happens. There are a lot of steps between "random planet with the right ingredients for life" and "vast interstellar empire."

Hanson broke it down into nine separate jumps that life requires to go from the little to the big leagues: the right star system, reproductive molecules, prokaryotic life, eukaryotic life, sexual reproduction, multicellular life, some vague category of intelligence (like using tools), advanced civilization with the potential for colonization and, finally, once all the pieces are in place, a gigantic galaxy-spanning explosion of life.

So where's the bottleneck? Is it at the beginning, with life-ready systems hard to come by? Is it somewhere in the middle, where life never gets a start or just spends billions of years swimming around in oceans? Or is it toward the latter stages?

From what we can observe, the ingredients for life are incredibly common in the universe, so it's unlikely that the filter is there. As for the appearance of simple life, we have only one example to go on — but we do know that as soon as the conditions for life were possible on Earth, life appeared. This suggests life may be more common than we think.

As for the appearance of intelligence, we know that our kind of intelligence emerged only once in the history of life on Earth and that it took billions of years to show up. So again, from this one solitary data point, it seems that simple life may be common, but intelligence is rare. So maybe that's the filter: It's hard to evolve intelligent beings.

But if intelligence is common, then we have a lot to worry about. That means it's easy for intelligent species to arise on a planet, but something stops them from going galactic. That could be either the universe doing the job — say, a giant asteroid wiping them out — or, more likely, the species destroying itself. That's because any species that can travel into space must be able to harness incredible amounts of energy — energy that could very easily be turned to destructive purposes before that species has learned to live on other worlds.

The Great Filter is not the only potential solution to the Fermi paradox, and even within the context of the Great Filter, humanity's fate is not sealed. Perhaps galactic colonization is harder than we think or is boring for reasons we haven't realized yet. Maybe progress isn't linear, and our future technological development will focus us inward. Or perhaps we're already on the other side of the filter, we are one of the few species to make it to this stage, and the galaxy is essentially our cosmic playground.

But seriously, where is everybody?

The most recent stop on its Red Planet road trip? A roughly 656-foot-long (200 meters) outcrop named Pico Turquino.

But it's not all fun and games for the Mars rover. Perseverance has been studying the local regolith and nearby geological features with its Mastcam-Z and SuperCam instruments from its location near Pico Turquino. And soon, the six-wheeled robot will move on to abrasion testing at the site, scratching the surface of some of the rocks in this photo to study their composition and structure.

Through this work, the Perseverance science team hopes to unearth geologic evidence that either predates or is related to the impact that formed the 28-mile-wide (45 kilometers) Jezero Crater — and potentially collect samples for NASA's planned Mars Sample Return campaign. Ultimately, Perseverance is searching for signs of possible life on Mars, and perhaps the rocks at Pico Turquino might hold some clues.

Related: NASA's Perseverance rover begins ambitious ascent up a Mars crater rim

This current quest is part of Perseverance's Crater Rim Campaign, the rover's fifth scientific effort on Mars, and what NASA officials have suggested might be "the most ambitious campaign the team has attempted so far."

The journey began in August, when Perseverance left the Neretva Vallis region to make the roughly 1,000-foot (305 m) climb to the top of Jezero's rim. And for months, the rover has delicately maneuvered up the difficult terrain of brittle crust; the rim's upper portion has a slope of about 20 degrees and is covered by slippery sand and dust.

Along the way, Perseverance has stopped to inspect exposed rocks, as it's doing at Pico Turquino. And it will continue to do so as it makes its way to the summit.

The rover's next science target is Witch Hazel Hill, but before arriving there, it'll pass through a high point at Lookout Hill. From there, the team anticipates pretty spectacular views both of Jezero Crater and the terrain beyond. Stay tuned for more photos from Perseverance!

The results hint that Ceres may have enough internal water, organic molecules, and the energy source needed for life to exist on the dwarf planet. Of course, that alone doesn't suggest the dwarf planet is inhabited.

Dawn was a mission that explored Ceres, the largest object in the main asteroid belt between Mars and Jupiter, and the slightly smaller Vesta. It beamed its last data back to Earth 6 years ago, but prior to that, in 2017, the spacecraft detected organic compounds near the Ernutet crater in Ceres' northern hemisphere.

Researchers from Spain's Instituto de Astrofísica de Andalucía used Dawn data to identify 11 more regions on Ceres rich in organic material. This indicated to the team that a reservoir of organic materials exists within Ceres.

With a width of over 578 miles (930 kilometers), Ceres doesn't quite meet the criteria of a planet, but with its abundant water, it could well qualify as an ocean world.

That means it is also an object with potential significance in the search for life beyond Earth.

Ceres: Inside and out

There was already heated discussion surrounding Ceres' origin and evolution, and this discovery may settle that debate.

The problem arises from the fact that organic compounds are rapidly degraded by solar radiation, and if these materials were always on the surface of Ceres, they should have been destroyed or at least have their abundances reduced.

One suggestion proposed that the detected materials were delivered to Ceres via recent impacts of organic-rich comets or asteroids. Another suggests that the organics seen at the surface of Ceres came from within the dwarf planet.

These findings dispute the former theory, suggesting the organic materials come from within the dwarf planet or are "endogenous."

"The significance of this discovery lies in the fact that, if these are endogenous materials, it would confirm the existence of internal energy sources that could support biological processes," team leader and Instituto de Astrofísica de Andalucía researcher Juan Luis Rizos said in a statement.

To investigate the organic compounds found on Ceres, the team used a new approach that examined the dwarf planet's surface and the distribution of organic matter at the highest possible resolution.

Of particular interest were the compounds discovered in a region at the equator of Ceres called the Ernutet crater. Most of the 11 regions discovered in the Dawn data were found in this region toward the equator of Ceres.

The materials in the sites around the Ernutet crater had been exposed to more solar radiation than those in the crater. That degraded the spectral features of the exposed material, making them tougher to spot in Dawn data.

Standing out to the team was a region between the Urvara and Yalode basins of Ceres, which contained the strongest traces of organic materials, which appear to have been dispersed through this region by the asteroid impacts that created these basins.

"These impacts were the most violent Ceres has experienced, so the material must originate from deeper regions than the material ejected from other basins or craters," Rizos said.

The scientist added that if the presence of organics is confirmed, their origin leaves little doubt that these compounds were created in the interior of Ceres.

And the quantities of the materials detected by the team hint that organic molecules must exist in great amounts below the surface of Ceres.

Ceres: Past, present, and future

The composition of Ceres links the dwarf planets with a family of meteorites rich in compounds of carbon. These fragments of asteroids are called "carbonaceous chondrites" which are thought to be composed of material that existed around 4.6 billion years ago as the planets were forming around the infant sun.

In addition to this, Ceres could be a vital destination for future space exploration.

"Ceres will play a key role in future space exploration. Its water, present as ice and possibly as liquid beneath the surface, makes it an intriguing location for resource exploration," Rizos explained. "In the context of space colonization, Ceres could serve as a stopover or resource base for future missions to Mars or beyond."

These researchers' findings, suggesting that organic materials were recently released to the surface of Ceres by asteroid impacts, are supported by separate results delivered by a team of Italian scientists.

This separate team found that organic compounds degrade more rapidly under solar radiation than previously estimated.

"The idea of an organic reservoir in such a remote and seemingly inert location like Ceres raises the possibility that similar conditions could exist on other solar system bodies," Rizos concluded. "Without a doubt, Ceres will be revisited by new probes in the near future, and our research will be key in defining the observational strategy for these missions."

The team's results were published in the Planetary Science Journal.

If humanity ended up in such a situation today, our best bet may be to turn to research uncovering how artificial intelligence (AI) develops languages.

But what exactly defines a language? Most of us use at least one to communicate with people around us, but how did it come about? Linguists have been pondering this very question for decades, yet there is no easy way to find out how language evolved.

Language is ephemeral, it leaves no examinable trace in the fossil records. Unlike bones, we can't dig up ancient languages to study how they developed over time.

While we may be unable to study the true evolution of human language, perhaps a simulation could provide some insights. That's where AI comes in — a fascinating field of research called emergent communication, which I have spent the last three years studying.

To simulate how language may evolve, we give agents (AIs) simple tasks that require communication, like a game where one robot must guide another to a specific location on a grid without showing it a map. We provide (almost) no restrictions on what they can say or how — we simply give them the task and let them solve it however they want.

Because solving these tasks requires the agents to communicate with each other, we can study how their communication evolves over time to get an idea of how language might evolve.

Related: Father-daughter team decodes 'alien signal' from Mars that stumped the world for a year

Similar experiments have been done with humans. Imagine you, an English speaker, are paired with a non-English speaker. Your task is to instruct your partner to pick up a green cube from an assortment of objects on a table.

You might try to gesture a cube shape with your hands and point at grass outside the window to indicate the color green. Over time you'd develop a sort of proto-language together. Maybe you'd create specific gestures or symbols for "cube" and "green". Through repeated interactions, these improvised signals would become more refined and consistent, forming a basic communication system.

This works similarly for AI. Through trial and error, they learn to communicate about objects they see, and their conversation partners learn to understand them.

But how do we know what they're talking about? If they only develop this language with their artificial conversation partner and not with us, how do we know what each word means? After all, a specific word could mean "green", "cube", or worse — both. This challenge of interpretation is a key part of my research.

Cracking the code

The task of understanding AI language may seem almost impossible at first. If I tried speaking Polish (my mother tongue) to a collaborator who only speaks English, we couldn't understand each other or even know where each word begins and ends.

The challenge with AI languages is even greater, as they might organise information in ways completely foreign to human linguistic patterns.

Fortunately, linguists have developed sophisticated tools using information theory to interpret unknown languages.

Just as archaeologists piece together ancient languages from fragments, we use patterns in AI conversations to understand their linguistic structure. Sometimes we find surprising similarities to human languages, and other times we discover entirely novel ways of communication.

These tools help us peek into the "black box" of AI communication, revealing how artificial agents develop their own unique ways of sharing information.

My recent work focuses on using what the agents see and say to interpret their language. Imagine having a transcript of a conversation in a language unknown to you, along with what each speaker was looking at. We can match patterns in the transcript to objects in the participant's field of vision, building statistical connections between words and objects.

For example, perhaps the phrase "yayo" coincides with a bird flying past — we could guess that "yayo" is the speaker's word for "bird". Through careful analysis of these patterns, we can begin to decode the meaning behind the communication.

In the latest paper by me and my colleagues, to appear in the conference proceedings of Neural Information Processing Systems (NeurIPS), we show that such methods can be used to reverse-engineer at least parts of the AIs' language and syntax, giving us insights into how they might structure communication.

Aliens and autonomous systems

How does this connect to aliens? The methods we're developing for understanding AI languages could help us decipher any future alien communications.

If we are able to obtain some written alien text together with some context (such as visual information relating to the text), we could apply the same statistical tools to analyze them. The approaches we're developing today could be useful tools in the future study of alien languages, known as xenolinguistics.

But we don't need to find extraterrestrials to benefit from this research. There are numerous applications, from improving language models like ChatGPT or Claude to improving communication between autonomous vehicles or drones.

By decoding emergent languages, we can make future technology easier to understand. Whether it's knowing how self-driving cars coordinate their movements or how AI systems make decisions, we're not just creating intelligent systems — we're learning to understand them.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

Long-lived civilizations may have many motivations for wanting to move somewhere else in the galaxy. They may need to escape an impending supernova, for example. Maybe they need to scout our new natural resources. Or maybe they just feel like exploring.

Given the enormous distances between the stars, however, interstellar travel is tremendously difficult and time-consuming. So, instead of leaving their system, an intrepid alien species might decide to take their system with them. The main advantage of accelerating their own star would be that they get to keep it with them as they travel. They would do this by causing their star to either radiate or evaporate in just one direction, which would propel the star, along with all of its planets, to a new location in the galaxy.

Astronomers have investigated whether "hypervelocity" stars (which, as their name suggests, are stars with an extraordinarily high velocity) may have been purposefully launched by alien civilizations, but the known candidates show no signs of artificial interference.

Related: Astronomers Detect a Swarm of Tiny Objects Orbiting an Alien Sun

In a recent paper, Clement Vidal, a philosopher at the Vrije University Brussels in Belgium, pointed out that most stars are not solitary but rather belong to binary systems. This means we might be missing half of the potential artificially accelerated stars. Even better, binary systems offer many advantages over their solo counterparts, Vidal wrote in his paper, which has not been peer-reviewed or published in a scientific journal.

Vidal took a model system consisting of a neutron star with a low-mass star tightly orbiting it. This setup provides the most flexibility in steerability and thrust.

The alien civilization would have to figure out a way to eject material from the star. This could be from asymmetric magnetic fields or from some device that causes uneven heating on the stellar surface. No matter what, the goal would be to get the star to eject more material in one direction than another. This would create thrust, pushing the binary system in the opposite direction, Vidal explained.

If the civilization were to place the machinery on or near the neutron star, where the strong gravity could provide a ready source of energy, they could steer the binary system by carefully cycling the machine off and on. For example, if they activated the machine only at the exact same point in the orbit, they would send the binary system in one direction. If they left the machine activated slightly longer, they would adjust their course, pointing their movement in any direction they wished along the orbital plane.

They could even steer their system in new off-orbit directions by altering the direction in which their machine was pointed, effectively changing the orbit of the neutron star around its companion.

Amazingly, there are real systems in the universe that match these kinds of characteristics, like the "black widow" pulsar PSR J0610-2100 and the "redback" pulsar PSR J2043+1711. Both of those systems have significant accelerations. Although they are unlikely to be caused by alien engineering, they are worth looking into, Vidal concludes. At least, while they're still around.

Launched on Oct. 14, the Europa Clipper spacecraft is currently en route to study Jupiter's icy moon Europa, which is believed to harbor a subsurface ocean. The mission lifted off from NASA's Kennedy Space Center in Florida atop a SpaceX Falcon Heavy rocket. It has since ventured 13 million miles (20 million kilometers) from Earth, traveling at a speed of 22 miles per second (35 kilometers per second) relative to the sun, according to a statement from NASA.

"Europa Clipper is the largest spacecraft NASA has ever developed for a planetary mission," NASA officials said in the statement. "It will travel 1.8 billion miles (2.9 billion kilometers) to arrive at Jupiter in 2030 and in 2031 will begin a series of 49 flybys, using a suite of instruments to gather data that will tell scientists if the icy moon and its internal ocean have the conditions needed to harbor life."

The spacecraft has so far operated as expected, having deployed its massive solar arrays shortly after launch. The solar arrays, which extend the length of a basketball court, collect sunlight to power the spacecraft on its journey to Jupiter, and during its science work in the Jovian system.

Related: SpaceX Falcon Heavy rocket launches NASA's Europa Clipper probe to explore icy Jupiter ocean moon (video)

Recently, the magnetometer's boom and several antennas for the spacecraft's radar instrument were deployed and will remain extended from the spacecraft for the full duration of the mission.

Measuring 28 feet (8.5 meters), the boom uncoiled from a canister mounted on the spacecraft body. Sensors paired with the hardware confirmed the deployment was successful. Once the spacecraft reaches Jupiter, the magnetometer will be used to measure the magnetic field around Europa. This will help scientists confirm the existence of the ocean believed to lie beneath the moon's icy crust and measure its depth and salinity, according to the statement.

The radar instrument includes four high-frequency antennas that extend crosswise from the solar arrays, each measuring 57.7 feet (17.6 m) long, and eight rectangular very-high-frequency antennas, each 9 feet (2.76 m) long. Engineering data transmitted back from the spacecraft allows the mission team to assess how the hardware is operating.

"It's an exciting time on the spacecraft, getting these key deployments done," Jordan Evans, Europa Clipper project manager from NASA's Jet Propulsion Laboratory in Southern California, said in the statement. "Most of what the team is focusing on now is understanding the small, interesting things in the data that help them understand the behavior of the spacecraft on a deeper level. That's really good to see."

The team will continue to check the spacecraft's hardware, with seven more instruments expected to power on and off in a series of tests planned for December and January.

To reach Jupiter, Clipper will perform a few gravity assists by looping around Mars and then back around Earth. This maneuver allows the spacecraft to leverage a planet's gravitational pull to gain speed and alter its trajectory.

The first Mars gravity assist is slated for March 1, 2025, when scientists plan to do a few tests of the radar instrument and turn on the spacecraft's thermal imager to capture multicolored images of Mars. The spacecraft will then swing by Earth in December 2026 to propel it further toward Jupiter. The team will use that final gravity assist around Earth to calibrate the magnetometer and measure our planet's magnetic field, according to the statement.