Perseverance Sample May Contain Potential Biosignatures, NASA Says

NASA’s Perseverance rover has collected a rock sample that a new paper in Nature describes as containing a “potential biosignature,” a finding officials called the closest the agency has come to evidence of ancient life on Mars.

Perseverance drilled the sample from a roughly 3.2-foot-long rock nicknamed Cheyava Falls in a quarter-mile-wide river valley in Jezero crater, the basin the rover has been exploring since landing in February 2021. The spacecraft arrived at that site in July 2024 after traveling about 18 miles westward following the crater’s former delta and riverbed features.

The rock displays streaks of red, green, purple and blue and is peppered with small, dark “poppy-seed” dots and larger dull yellow “leopard spots,” according to the Nature paper and presentations by team scientists. Onboard X-ray and laser instruments indicate the colors correspond to different iron-, phosphorus- and sulfur-bearing materials. The rover’s analyses detected two iron-rich minerals, vivianite and greigite, that on Earth are commonly associated with organic matter and can be produced by microbial activity.

“This finding by Perseverance…is the closest we have ever come to discovering life on Mars,” acting NASA administrator Sean Duffy said in a statement released with the paper. Joel Hurowitz, lead author of the Nature paper and a member of the Perseverance science team, told reporters the combination of mud, organic matter and the minerals found in the rock resembles sediments on Earth where microbial metabolism leaves similar mineralogical fingerprints.

Perseverance did not detect fossilized or living microbes, and NASA and the authors emphasize that the term “potential biosignature” is precise and provisional. "Astrobiological claims, particularly those related to the potential discovery of past extraterrestrial life, require extraordinary evidence," Katie Stack Morgan, Perseverance’s project scientist, said in the agency’s statement. NASA defined a potential biosignature as "a substance or structure that might have a biological origin but requires more data or further study before a conclusion can be reached about the absence or presence of life." Hurowitz acknowledged at a Sept. 10 press briefing that nonbiological processes could produce similar features and that laboratory work on Earth and returned samples will be needed to rule those out.

The sample in question is one of dozens Perseverance has been storing in small titanium tubes on the Martian surface as part of a planned Mars Sample Return (MSR) campaign. The rover was launched with 43 empty tubes and has cached multiple cores and soil samples intended for retrieval by subsequent missions. Under long-standing plans, a fetch rover would collect the cached tubes, place them on an ascent vehicle that would launch them from Mars, and transfer them to an Earth-Return Orbiter built by the European Space Agency for delivery to laboratories on Earth.

Those follow-on missions have not been built, and MSR’s future is uncertain. In early May, President Donald Trump submitted a budget request that would cut NASA funding by about 24% and proposed canceling or scaling back several programs, including aspects of the sample-return effort. Congress must approve federal budgets, and at the Sept. 10 briefing Duffy said NASA is reviewing budgets and timelines while considering alternative technologies to retrieve samples more quickly. "What we're going to do is look at our budgets," he said. "We're going to look at our timing. And, you know, how do we spend money better? And what technology do we have to get samples back more quickly?"

Scientists caution that laboratory analyses on Earth remain the only path to a definitive determination. Returned samples would allow for more sensitive chemical, isotopic and microscopic testing than instruments currently aboard Perseverance, and would enable experiments that can better exclude abiotic explanations for the observed minerals and textures.

Perseverance’s discovery adds to a growing body of evidence that Jezero crater once hosted a lake and river systems and that sedimentary environments there concentrated organic carbon and redox-reactive minerals. Prior work has established that ancient Mars had environments that could have been habitable for microbial life. The new findings identify specific mineral assemblages, textures and organics in situ that warrant rigorous follow-up.

Until samples are returned and examined on Earth, the result will remain a carefully worded candidate rather than a confirmed detection of past life. In the meantime, the Perseverance team will continue to map and sample the crater, refine interpretations through laboratory analog studies on Earth and advocate for the hardware and funding needed to complete the long-planned sample-return campaign.

The Nature paper and NASA’s statements underscore both the scientific promise of the cached Martian material and the logistical and policy hurdles that must be overcome to test the tantalizing possibility that Mars once hosted microbial life.