Evidence for possible life on Mars in the ancient past continues to build, thanks to a recent discovery by NASA’s Perseverance rover that identified complex carbon in two mudstones.

As detailed in a recent paper published in Science Advances, Perseverance collected samples in the Jezero crater, a location that has continued to yield possible biosignatures of life on Mars in the ancient past.

In the same region, scientists reported potential evidence of microbial activity on ancient Mars, adding to a growing list of circumstantial evidence for one of the most intriguing possibilities in modern space exploration: the prospect that Earth may not have been the only planet in our Solar System that has held the potential to host life.

A Prime Location for Life on Mars

Among the study’s most significant findings is that complex macromolecular carbon was discovered alongside other potential biosignatures. Jezero Crater, a 28-mile-wide impact basin on the Martian surface, once contained flowing water roughly 3.5 billion years ago, making it one of the most promising locations in the search for ancient life. Water is essential to all known life on Earth, serving as a universal solvent and playing a critical role in biological processes.

“Jezero Crater was selected as a landing site due, in part, to its past evidence of aqueous activity and potential to preserve organic material,” co-lead author Kyle Uckert, a research scientist at NASA’s Jet Propulsion Laboratory, told The Debrief. “The Perseverance Rover’s exploration of Jezero Crater helps us understand the past habitability of Mars.”

Perseverance targeted a distinctive geological feature known as the Bright Angel outcrop, where the samples were collected. The outcrop consists of mudstones deposited in the dry bed of an ancient river that once flowed into Jezero Crater. Comparable sedimentary deposits on Earth are often associated with environments capable of preserving evidence of microbial life.

Analyzing Samples

Determining the origin of the organic carbon preserved within these Martian rocks is key to understanding whether the Red Planet ever supported life.

Using its onboard Raman spectrometer, Perseverance mapped the distribution of the rocks’ organic matter. One sample contained organic carbon within a primary silicate-dominated matrix, while another preserved carbon within secondary carbonate and sulfate minerals.

Notably, the carbon appears to have remained remarkably well preserved despite billions of years of exposure to the harsh Martian environment. Researchers suggest its limited weathering may indicate that the material is resistant to radiation and oxidation—possibly because it is mixed with iron-rich regolith or protected by clay minerals—or that it was only recently exposed at the surface through erosion.

The researchers are quick to point out that their findings do not determine whether the carbon originated through biological or non-biological processes. Nevertheless, the discovery adds another intriguing piece of evidence to the ongoing search for ancient life on Mars.

“Macromolecular carbon may be delivered to Mars via meteorites, or may have formed through hydrothermal geologic processes,” Uckert said.

Continuing to Explore Life on Mars

According to the researchers, determining the true origin of the carbon will ultimately require returning Martian samples to Earth, where they can be examined using far more sophisticated laboratory instruments than those carried aboard Perseverance.

“Further constraining the origin, distribution, and alteration history of the MMC observed in the Neretva Vallis mudstones requires high-resolution and high-sensitivity analyses in terrestrial laboratories, which can be facilitated by the return of the Cheyava Falls rock core, ‘Sapphire Canyon’ to Earth,” explained co-lead author Ashley Murphy, a postdoctoral research scientist at the Planetary Science Institute.

“The Perseverance Rover science payload is not designed to determine whether martian organic molecules were created by biologic or geologic processes, and our study is unable to make this distinction,” Uckert added.

The researchers say that future sample-return missions, combined with advanced laboratory analyses on Earth, may finally help resolve one of planetary science’s most enduring questions.

“The Perseverance Rover collects samples of scientifically compelling martian rocks for potential return to Earth,” Uckert concludes.“Using high-resolution terrestrial instruments to analyze these rock samples, particularly the Sapphire Canyon core collected on the Cheyava Falls rock, may provide more compelling evidence for a biologic or abiotic origin of this organic matter.”

The paper, “Spatially Distributed Complex Organic Matter Detected in an Ancient River Valley in Jezero Crater, Mars,” appeared in Science Advances on June 24, 2026.

Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.

Earth has many unique features for a planet, such as a magnetic field, a large moon, and plate tectonics. It’s also the only planet we know of that harbors life. These facts form the basis of the Rare Earth hypothesis, which posits that we haven’t found aliens because other planets in the Galaxy probably don’t have all the right conditions for life. 

Another characteristic of Earth is that about 30% of its surface is land and about 70% is ocean. Recently, Columbia University Assistant Professor David Kipping investigated whether the proportion of Earth’s surface covered by dry land versus ocean, or its land fraction, is another reason Earth is habitable not only for simple single-celled organisms, but also for intelligent species like humans. 

To test this hypothesis, Kipping created 4 statistical models of planets with different land fractions that intelligent aliens could potentially evolve on. First, he created an equation to describe the likelihood that a planet in its star’s habitable zone has a particular land fraction, known as a probability distribution. Kipping weighted this probability distribution toward the extreme ends, making it more likely that a planet would be covered by a single huge landmass or a single vast ocean than by a mix of both, as on Earth. 

Kipping then incorporated this land fraction probability distribution into his statistical models to calculate the probability that a random planet will have that land fraction and host intelligent life. The 4 scenarios Kipping tested were: 1) that intelligent life is more likely to emerge on land-dominated planets, 2) that it’s more likely to emerge on ocean-dominated planets, 3) that it’s more likely to emerge on planets with roughly equal amounts of land and ocean, and 4) that its emergence is independent of a planet’s land fraction. 

As a first step in determining the kinds of planets intelligent aliens would tend to emerge on, Kipping used each model to predict the probability that intelligent life would emerge on a planet with the same land fraction as Earth. He then compared these probabilities by calculating the ratios between each value. Because Earth is the only known planet with intelligent life, a model that predicted a greater probability for humanity’s existence on Earth would be more likely to reflect reality.

Kipping considered it strong evidence that a given model was more realistic than another if the ratio between 2 of them was greater than 10, meaning one model was 10 times more likely to predict the existence of Earth and humanity. Kipping found that no comparison of any 2 models passed this threshold. However, the models assuming that intelligent life prefers ocean-dominated planets or planets with a land-ocean balance were 2.5 and 3 times more likely to predict the existence of humanity than the model assuming that intelligent life prefers land-dominated planets. Additionally, the model assuming that intelligent life prefers a land-ocean balance was always more likely to predict humanity than any other model, though marginally. 

Kipping also addressed whether finding more planets with intelligent life would affect which model was deemed most realistic, for example, if scientists discovered conclusive evidence of life on Mars in its distant past. Here, Kipping identified 2 complications. First, it’s uncertain how much of Mars’s surface was once covered by water – some estimate it had a land fraction as high as 81%, while others estimate it was as low as 25%. Second, proving that Mars once had life would not prove it once had intelligent life.

Regardless, Kipping reran the models assuming that ancient Mars had a land fraction comparable to Earth’s. Adding this second data point produced ratios similar to those in the earlier Earth-only calculations, meaning it still didn’t make any single model 10 times more likely to predict the existence of humans and Martians, respectively. 

Kipping then took the 10-times threshold and reversed the calculations to find what conditions would exceed it. In doing so, he calculated that astronomers would need to find 14 other planets with intelligent life and known land fractions to robustly determine whether intelligent life is more likely to occur on desert planets, ocean planets, balanced planets, or without bias.

Kipping concluded that he can’t yet definitively state whether there is something special about Earth’s land fraction when it comes to producing intelligent species. However, Earth’s existence would suggest that intelligent life is unlikely to favor extreme desert planets, so the Milky Way probably isn’t filled with Tatooines and Jakkus. And while his analysis doesn’t debunk the Rare Earth hypothesis, it does undermine the argument that Earth’s ocean size explains why Earth is rare. 

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Most people think of Mars as a big red dustball, but researchers recently found Martian mineral deposits suggesting it was once warm and humid. The team used the Compact Reconnaissance Imaging Spectrometer aboard NASA’s Mars Reconnaissance Orbiter to analyze specific wavelengths of visible and near-infrared light from minerals on Mars’s surface to determine their chemical composition from afar.

Past researchers identified layered silicate minerals, called clays, across the Martian surface. Clays form when water interacts with rock, and record the amounts and chemical compositions of the waters that formed them. As water interacted with Martian surface rocks, it picked up more mobile elements like magnesium and iron and carried them to lower depths in the Martian soils, while less mobile elements like aluminum stayed in place. This process, called leaching, created 2 distinct layers of clays in the Martian rocks. 

Scientists have proposed 2 main hypotheses for how these layered clays formed on Mars. The first is that they formed through underwater leaching in pools or lakes sometime in Mars’ past. The second is that they formed across the Martian surface, where a widespread humid environment provided the moisture needed to leach them. 

To evaluate these hypotheses, a team led by researchers at Purdue University recently estimated the “true” thicknesses of Martian clay layers with a method scientists had previously only used on Earth. Rock layers containing clays can become tilted, making them appear thicker or thinner than they actually are. To address this discrepancy, the team used the High Resolution Imaging Science Experiment (HiRISE) tool on the Mars Reconnaissance Orbiter to create high-resolution elevation maps of the Martian surface. Then they combined these maps with surface composition data from the Compact Reconnaissance Imaging Spectrometer to create 3D composition maps. 

Using the 3D composition maps, the researchers found where each clay layer was exposed at the surface and traced it underground to estimate an angle of tilt. They then used trigonometry to calculate the true thicknesses of each clay layer. They analysed 46 regions across the Martian surface, and found that the combined thickness of both clay layers was around 20 to 680 feet (6 to 200 meters), with an average of about 190 feet (60 meters). That’s a maximum thickness as high as a 60-story building! 

Next, the researchers tested the extent of the clay deposits in a large ancient Martian valley known as the Mawrth Vallis Region. They focused on this region because it had large elevation changes, and scientists in the past had already collected high-resolution chemical composition and elevation data there. 

They explained that if the clay layers were restricted to the lowest parts of the valley where water once existed, and had changing thicknesses and boundaries between layers, this would provide strong evidence in favor of the “underwater leaching” hypothesis. In contrast, if the clay layers were more widespread, with consistent layer boundaries and thicknesses, this would provide strong evidence of a humid surface environment, in favor of the “surface leaching” hypothesis. 

The researchers found that the clay layers extended beyond the lowest parts of the valley and had consistent layer boundaries across more than half a mile (about a kilometer) of elevation change. Thus, they concluded that the clay layers formed by surface leaching in a humid environment. 

These findings conflict with climate models of early Mars, which generally suggest that the Martian surface rarely got above freezing temperatures. To address this discrepancy, the team proposed that these deposits could have formed over a long period of time rather than in a consistently warm and wet environment. If the surface was frozen most of the time, but got above freezing in short bursts, these clay deposits could still have formed, just over a much longer time period. In this case, the Mars climate models and the researchers’ findings would agree.

The researchers acknowledged that their study has some limitations, particularly regarding the sparse sample locations. Though they found strong evidence for a widespread humid environment on early Mars, more in-depth studies of locations like Mawrth Vallis could better constrain the specific surface environmental conditions under which these clays formed and potentially reconcile their data with Martian climate models.

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