Life on Mars: What Scientists Have Found So Far

May 19, 2026

Pillar page: Astrobiology: The Search for Extraterrestrial Life

Introduction

Of all the questions humanity has ever asked, few carry more weight than this one: are we alone in the universe? And of all the places in the solar system where that question might find an answer, none holds more promise — or has generated more controversy — than Mars.

The Red Planet sits roughly 225 million kilometres from Earth on average, close enough for our rovers to reach but distant enough that every discovery takes months to verify and years to publish. Yet the pace of revelations has been accelerating. In September 2025, NASA announced what its own administrator called “the closest we have ever come to discovering life on Mars” — a potential biosignature locked inside an ancient Martian rock, published in the journal Nature after a year of painstaking scientific scrutiny.

This is not a fringe claim. It is peer-reviewed science from the most sophisticated planetary rover ever built, analysing samples from one of the most promising geological sites on Mars.

This article walks through everything scientists have found — from the first hints of ancient water to the extraordinary chemistry of Cheyava Falls — and explains what it all means for the biggest question in science.

Why Mars? The Case for a Once-Habitable World

Mars today is hostile to life as we know it. Its surface temperature averages -60°C. Its atmosphere is 95% carbon dioxide and barely 1% as thick as Earth’s — too thin to shield the surface from lethal ultraviolet radiation. Liquid water cannot exist on the surface under current conditions; it would instantly evaporate or freeze.

But Mars was not always like this.

Between 3 and 4 billion years ago, Mars had a dramatically different character. Geological evidence — visible from orbit and confirmed on the surface — shows that liquid water flowed across Mars in vast quantities. Ancient river valleys, dried lake beds, delta formations, and mineral deposits that only form in the presence of water tell a coherent story: early Mars was warmer, wetter, and had a thicker atmosphere capable of sustaining liquid water on its surface for potentially millions of years.

This window of habitability — what scientists call the Noachian and Hesperian periods — coincides almost precisely with the period on Earth when life first emerged. On our planet, life arose in liquid water roughly 3.5 to 4 billion years ago. If the same chemistry was unfolding on ancient Mars at the same time, the question is not whether life could have existed there. The question is whether it actually did — and whether any trace of it survived.

That is what the current generation of Mars missions is designed to answer.

The Evidence So Far: A Timeline of Discovery

The Viking Landers (1976) — The First Attempt

The story of the search for Martian life begins not with a rover but with NASA’s twin Viking landers, which touched down on Mars in 1976. They carried the first biology experiments ever conducted on another planet — including one that added liquid nutrient solution to Martian soil and looked for signs of metabolic activity.

The result was ambiguous and remains controversial to this day. One experiment — the Labelled Release experiment, designed by Gilbert Levin — produced a positive signal consistent with microbial respiration. But other Viking experiments found no definitive organic molecules in the soil, which NASA interpreted as evidence that the reaction was chemical rather than biological.

Levin maintained until his death in 2021 that the Viking results were consistent with life. The scientific mainstream remained unconvinced, partly because subsequent research showed that Martian soil contains highly reactive chemicals called perchlorates that can mimic biological reactions and destroy organic molecules — which may explain why the other Viking instruments missed organics that were present.

The Viking legacy is this: we have been tantalisingly close to an answer for fifty years.

Curiosity Rover: Organic Molecules and Mysterious Methane (2012–present)

NASA’s Curiosity rover landed in Gale Crater in August 2012 and has been transforming our understanding of Mars ever since. Its most significant contributions to the life question fall into two categories.

Ancient organics. In 2018, Curiosity’s SAM (Sample Analysis at Mars) instrument detected complex organic molecules — carbon-based chemical compounds — preserved in 3-billion-year-old sedimentary rocks near the surface of Gale Crater. These are the building blocks of life. While organic molecules can form through non-biological processes, finding them preserved in ancient rocks is a crucial prerequisite for any search for past life. NASA’s Curiosity project scientist Ken Farley noted at the time that finding organics in surface rocks makes it “more likely that — if there is indeed a record of ancient life on Mars — it may have been preserved.” You can explore the broader context of these findings at the NASA Mars Exploration Program page.

Seasonal methane. Curiosity also detected seasonal variations in atmospheric methane — a gas that, on Earth, is overwhelmingly produced by living organisms. The methane appeared to peak in Martian summer and diminish in winter, a pattern suggestive of an active source. However, methane can also be produced by geological processes, and a 2025 paper in the Journal of Geophysical Research raised questions about whether some of Curiosity’s methane readings might originate from the rover’s own onboard systems rather than the Martian atmosphere. The debate continues, and resolving it requires instruments that Curiosity was not designed to carry.

What Curiosity established beyond doubt is that Gale Crater — an ancient lake bed — contained all the chemical building blocks and energy sources necessary for microbial life billions of years ago. Mars was, at minimum, habitable.

Jezero Crater: Water, Minerals, and a Delta (2021–present)

NASA’s Perseverance rover landed in Jezero Crater in February 2021. The choice of landing site was deliberate and consequential. Jezero is the remnant of an ancient lake fed by a river system — and it contains a spectacularly preserved river delta, the fan-shaped deposit of sediment that forms where a river meets standing water.

On Earth, river deltas are exceptional repositories of biological material. Sediments settle slowly and trap organic compounds, creating exactly the conditions under which ancient life — if it existed — would most likely be preserved. Scientists had identified Jezero from orbit as one of the most promising sites on Mars for biosignature preservation before Perseverance ever launched.

The rover’s early findings confirmed and exceeded those hopes. By 2024, Perseverance had identified more than two dozen types of minerals in Jezero’s rocks, telling a story of multiple episodes of water activity — some involving hot, acidic fluids hostile to life, and others involving cooler, alkaline conditions far more hospitable. In September 2025, Rice University researchers publishing in a peer-reviewed journal reported that Jezero’s geological history showed a clear shift “from harsher, hot, acidic fluids to more neutral and alkaline ones over time — conditions we think of as increasingly supportive of life.”

Ground-penetrating radar confirmed that Jezero was indeed once a vast lake. The sedimentary fan deposit where Perseverance has been operating was laid down by flowing water. And in the rocks of that ancient riverbed, the rover found something extraordinary.

The Cheyava Falls Discovery: The Closest We Have Come

In July 2024, Perseverance was exploring the “Bright Angel” formation — a set of rocky outcrops along the banks of Neretva Vallis, an ancient river channel a quarter of a mile wide that once fed Jezero’s lake. The rover encountered an arrowhead-shaped rock measuring roughly one metre by 0.6 metres. Scientists named it “Cheyava Falls.”

What Perseverance found inside that rock, after drilling and analysing its freshly abraded surface with its PIXL (Planetary Instrument for X-ray Lithochemistry) and SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals) instruments, stopped the scientific world.

The leopard spots

The rock’s surface was marked by two kinds of unusual features: small dark dots the size of ultra-fine glitter, nicknamed “poppy seeds,” and larger splotches of lighter tones surrounded by dark rims — structures that the science team immediately dubbed “leopard spots.”

On Earth, rocks bearing almost identical patterns exist. Scientists know what makes them: microbes. Specifically, the patterns arise when microbial communities metabolise iron and sulphur compounds in oxygen-poor, water-saturated sediments, leaving behind characteristic mineral rings as chemical byproducts of their digestion. Researchers had predicted before Perseverance launched that exactly this kind of pattern — if it appeared on Mars — would be a compelling biosignature worth investigating.

The chemistry

Perseverance’s instruments found that the leopard spots were not random discolourations. They were composed of specific minerals arranged in repeating, structured patterns:

Vivianite — an iron phosphate mineral associated with biological activity in oxygen-poor environments on Earth
Greigite — an iron sulphide linked to microbial iron and sulphur cycling
Organic carbon — found co-located with the phosphate, iron, and sulphur in the same structured regions

The combination and arrangement of these compounds, as lead author Joel Hurowitz of Stony Brook University explained, “could have been a rich source of energy for microbial metabolisms.” The textures and chemistry were consistent with low-temperature reactions — the kind of conditions life can tolerate — rather than the high-temperature processes that would erase delicate biosignatures.

The significance — and the caution

In September 2025, NASA published these findings in the journal Nature. The official NASA statement described it as “the closest we have ever come to discovering life on Mars.” The paper represents the result of a full year of independent scientific scrutiny of the data.

Critically, the scientists could not identify a convincing non-biological explanation for all of the features observed simultaneously. But they were equally clear that this does not constitute proof of life. Science demands rigorous standards. A potential biosignature — which is what Cheyava Falls represents — is a substance or structure that might have a biological origin but requires more data before a definitive conclusion can be reached.

The rock’s sample, named “Sapphire Canyon,” has been sealed in one of Perseverance’s titanium tubes and is awaiting return to Earth. Laboratory instruments on our planet are orders of magnitude more powerful and precise than anything that can be sent to Mars. When — and if — that sample arrives in an Earth laboratory, scientists will be able to conduct tests that could definitively confirm or rule out a biological origin.

As Bethany Ehlmann, president of The Planetary Society and co-investigator on two of Perseverance’s science instruments, put it: “It’s exactly the type of sample that NASA, the European Space Agency, all of us for decades engineered the Perseverance rover to be able to find.”

For a deep dive into the standards of evidence used in the search for life, see The Planetary Society’s analysis of the Cheyava Falls discovery.

Other Lines of Evidence

Possible photosynthesis in ice

In October 2024, NASA announced a striking finding: it may be possible for photosynthesis to occur within dusty water ice exposed in the mid-latitude regions of Mars. Dust particles trapped within water ice can create localised warm spots where liquid water might transiently exist, and the filtered sunlight passing through ice could potentially support simple photosynthetic organisms — similar to algae that live inside glacial ice on Earth. This remains a hypothesis under investigation, not a confirmed finding, but it opens the possibility that life might not be entirely a thing of the past on Mars.

The methane mystery

The recurring detection of methane in the Martian atmosphere — by Curiosity on the surface and by the European Space Agency’s Mars Express orbiter from space — remains one of the most intriguing unresolved questions in planetary science. Methane is chemically unstable in Mars’s oxidising atmosphere and should break down within a few hundred years under ultraviolet radiation. If methane is present, something is actively producing it — either geological processes (serpentinisation, volcanic outgassing from ancient clathrates) or biological ones.

The ExoMars Trace Gas Orbiter, operated jointly by ESA and Roscosmos, has been mapping Martian atmospheric methane since 2018 to try to pinpoint its source. The results have been puzzling: the orbiter has sometimes failed to detect methane that Curiosity detected at the same time, suggesting the gas may be extremely localised and transient, or that one of the measurements has systematic errors. Resolving the methane mystery is one of the highest priorities for the next generation of Mars science. You can track the latest findings through the ESA Mars Express mission page.

Subsurface liquid water

In 2018, the ESA Mars Express radar instrument detected what appeared to be a 20-kilometre-wide reservoir of liquid water buried about 1.5 kilometres beneath the south polar ice cap. Subsequent studies using the same instrument found additional radar reflections that could be interpreted as multiple subsurface liquid water bodies. However, these findings remain controversial — some researchers argue the radar signatures could be produced by clay-rich sediments or other geological materials rather than liquid water.

If liquid water does exist beneath the Martian poles today — possibly kept liquid by a combination of salts lowering the freezing point and geothermal heat from below — it would represent not just a past habitable environment but a potentially currently habitable one.

The Mars Sample Return Problem

The most direct way to answer the life question is to bring Martian rocks to Earth. Perseverance has been methodically collecting and caching samples precisely for this purpose — as of mid-2025, it had filled 33 of its 43 sample tubes, including the potentially biosignature-bearing Sapphire Canyon tube from Cheyava Falls.

The planned Mars Sample Return mission, a joint NASA–ESA project, was designed to retrieve these samples and deliver them to Earth laboratories in the late 2020s or early 2030s. However, in 2025, the White House proposed slashing NASA’s science budget by 47%, threatening to cancel or delay Mars Sample Return along with numerous other missions.

The consequences of cancellation would be profound. The Cheyava Falls sample — potentially the most scientifically valuable material ever collected from another world — would remain stranded on Mars, unsealed and unstudiable by Earth’s most powerful instruments.

China’s Tianwen-3 mission, scheduled to launch in 2028, is aiming to return Mars samples to Earth independently of NASA. The race to bring Martian material home may ultimately determine which nation first holds the answer to whether Mars ever hosted life.

What Would It Mean to Find Life?

It is worth pausing to consider what a confirmed detection of life — even ancient, fossilised microbial life — on Mars would actually mean.

It would mean that life arose independently on at least two planets in the same solar system within a relatively short window of cosmic time. The statistical implication of that fact is staggering: if life can arise independently twice in a single solar system, it almost certainly arises throughout the universe wherever suitable conditions exist. The cosmos would not be vast and empty — it would be teeming with biology.

It would also raise a more unsettling question. Scientists call it the Fermi Paradox: if life is common in the universe, where is everyone? And a related concept called the Great Filter: is there some barrier — perhaps extinction, perhaps the difficulty of developing complex multicellular life — that most life-bearing worlds fail to cross? Knowing that Mars hosted microbial life but was eventually sterilised would suggest that early life is common but complex life is rare. Knowing that Mars never hosted life at all, despite having the right conditions, would suggest that even the origin of life is vanishingly difficult.

Either answer would be one of the most important facts our species has ever learned.

These questions connect directly to the broader field of astrobiology — the science of life’s potential in the cosmos — which you can explore in our pillar article on astrobiology and the search for extraterrestrial life.

What Comes Next

The search for life on Mars is entering its most critical phase. Several developments to watch:

Perseverance continues sampling. The rover was still active as of May 2026, venturing into some of the oldest geological terrain in the entire solar system. Every new rock analysed is a new data point. Further Cheyava Falls-like discoveries remain possible.

Mars Sample Return resolution. Whether the NASA–ESA mission survives its funding crisis — or whether China’s Tianwen-3 gets there first — the return of Martian samples to Earth would be transformative. Earth laboratories can perform isotopic analysis, search for cellular structures, and conduct experiments impossible on a rover.

ESA’s Rosalind Franklin rover. The ExoMars Rosalind Franklin rover, which carries a drill capable of reaching two metres below the Martian surface — below the zone sterilised by UV radiation — remains in development. If launched in the late 2020s, it would investigate subsurface environments that no mission has yet reached.

Human missions to Mars. Multiple space agencies and commercial operators have long-term human Mars missions in planning. Boots on the ground — and human geologists with contextual judgement that no remote-controlled robot can replicate — would fundamentally change the pace of discovery.

Conclusion

We have not yet found life on Mars. That much is clear. But we have found something almost as remarkable: compelling, peer-reviewed evidence that Mars was once habitable, that it harboured the chemical conditions for life, that organic molecules were preserved in ancient rocks, and that at least one rock — Cheyava Falls — contains structures and chemistry that are most easily explained by biological activity, even if non-biological explanations cannot yet be fully ruled out.

The evidence has been building in one direction for decades. Ancient water. Organic carbon. Seasonal methane. A potential biosignature that scientists spent a year trying to disprove — and could not.

Whether Mars harboured life remains an open question. But it has never been a more scientifically credible one.

External sources

NASA Mars Exploration Program — mission updates, rover data, and the full archive of Mars science results
The Planetary Society: Cheyava Falls deep dive — the most thorough independent analysis of the September 2025 biosignature announcement
ESA Mars Express mission — the European mission tracking Martian methane and subsurface water from orbit

James Webb Space Telescope: Discoveries That Are Rewriting Astronomy