NASA’s Perseverance Finds Rocks That Offer Strongest Hints Yet of Ancient Martian Microbes

NASA’s Mars rover Perseverance has uncovered sedimentary rocks in a dried river channel that contain organic carbon and tiny mineral features scientists say are among the most compelling potential signs yet of ancient microscopic life on Mars.

The sample, collected from reddish, clay-rich mudstones in Neretva Vallis — a channel that once carried water into Jezero Crater — contains minuscule specks enriched with iron phosphate and iron sulfide, along with traces of organic carbon, researchers reported Wednesday in the journal Nature. The features, described by the study team as “poppy seeds” and “leopard spots,” are chemically similar to mineral byproducts produced on Earth when microorganisms break down organic matter.

Joel Hurowitz, a geochemist at Stony Brook University and lead author of the new paper, cautioned that the rover cannot directly detect life and that laboratory analysis on Earth will be needed to test biological versus nonbiological explanations. “All we can say is one of the possible explanations is microbial life, but there could be other ways to make this set of features that we see,” he told The Associated Press.

Perseverance drilled into the outcrop, part of a sequence known as the Bright Angel formation, and sealed the material into a titanium sample tube that was left on the Martian surface for eventual retrieval. The tube was collected last summer and at the time represented the 25th sample gathered from Jezero; Perseverance’s sample tally has since risen to 30, with six more planned before the rover’s mission winds down.

On Earth, iron sulfide and iron phosphate enrichments often accompany microbial processes in sediments and certain lake environments, including Antarctic lakes where microbes interact with minerals under cold, low-oxygen conditions. Two scientists who were not involved in the study — Janice Bishop of the SETI Institute and Mario Parente of the University of Massachusetts Amherst — wrote in an accompanying editorial that nonbiological chemical processes could also produce the observed mineral assemblages and that laboratory study of the returned samples will be essential.

“The result is an exciting discovery,” Bishop and Parente wrote, while emphasizing that alternative explanations must be carefully evaluated. Hurowitz called the finding “the best, most compelling candidate yet” in Perseverance’s search for potential signs of long-ago life, but said definitive conclusions will require detailed analyses that can only be performed in terrestrial laboratories.

Perseverance, launched in 2020 and operating on Mars since 2021, was designed to drill and cache rock samples in sealed tubes for a planned return to Earth. The anticipated sample-return campaign, once planned for the early 2030s, has been delayed into the 2040s amid escalating costs and complexity; NASA estimates the effort could reach roughly $11 billion. Ten spare titanium sample tubes were intentionally placed on the Martian surface some years ago as contingencies for the still-evolving retrieval plan.

Until the samples are transported to Earth by a future robotic mission or by astronauts, researchers must rely on in situ instrument readings and Earth-based analog studies and experiments to assess whether ancient Martian environments could have hosted microbial life. The team emphasized there is no evidence of life on Mars today, and that any biological interpretation pertains to conditions billions of years ago when Jezero Crater hosted water and deposited the sediments now under study.

The Nature paper provides a detailed geochemical and petrographic description of the Bright Angel mudstone and the iron-rich microfeatures. The authors say the sedimentary context — a former river channel that fed a crater lake — and the preservation of both organics and iron minerals make the material a promising target for future laboratory assays aimed at distinguishing biological signatures from abiotic mineralization.

If returned and confirmed as biological in origin, the samples would represent the first conclusive evidence of past life beyond Earth. The researchers and outside commentators stressed that the current findings fall far short of that threshold but represent a meaningful step in selecting and characterizing samples most likely to preserve any record of ancient microbial activity on Mars.

For now, the discovery underscores both the scientific potential of Perseverance’s cached collection and the importance of completing a reliable sample-return strategy that can bring Martian material to Earth-based laboratories for the rigorous analyses needed to resolve the question of ancient life on Mars.