The Perseverance Rover Spotted A Rock That May Be The Strongest Sign Of Ancient Life Yet

NASA's Perseverance rover has been exploring Mars' Jezero Crater since 2021 with the primary objective to investigate the environments that could have supported life in the past on the Red Planet. In order to do that, the rover is busy collecting samples for possible return to Earth, where they can be meticulously studied. Jezero Crater was the obvious choice for research because orbital data revealed evidence of abundant water in ancient times; there's an old (now dry) river delta that used to supply Jezero Crater with water. After all, the name Jezero, in some Slavic languages, means "lake." What's more, this former lake might have just done a lot to help Perseverance find signs of ancient Martian life – rocks with strange patterns potentially created by organic reactions.

During the survey of the crater floor and the feeder valleys, the rover encountered sedimentary rocks with distinctive surface textures. One of the most notable examples featured round, dark-toned markings scattered against pale mudstone. The scientists referred to this pattern as "leopard spots", but there's more to them. Their resemblance to the mineral structures seen in some Earth environments suggests they're the result of redox reactions involving sulfur, iron, and phosphorus. In a terrestrial setting, such a reaction can be driven by either abiotic chemistry or microbial activity.

The presence of these leopard spots on the Martian rock is astonishing, but research in this area is far from finished. While Perseverance can document the morphology, mineralogy, and chemistry of the samples on site, determining whether these features are a representation of biological activity or purely geochemical processes requires laboratory analyses on Earth.

In July 2024, NASA's Perseverance rover extracted a core sample from a rock dubbed Cheyava Falls, located in the Bright Angel region of Jezero Crater. The extracted sample, referred to as "Sapphire Canyon," has become the centerpiece of a study published in Nature in September 2025. The study, led by Joel Hurowitz of Stony Brook University, argues that this sample contains potential biosignatures. A "potential biosignature," as defined in a recent NASA/JPL release, is a structure, substance, or chemical pattern that might be of biological origin, but which require further substantiation to confirm past or present life.

The study reports that Sapphire Canyon exhibits mineral and chemical attributes that, on Earth, are often associated with microbial activity. These include  carbon-bearing mudstones, along with spotted textures. The so-called "leopard spots" are composed of iron phosphate and iron sulfide minerals that are found near — or created by — organic life here on Earth. Granted, these minerals can be formed via abiotic processes, but those rely on high heat. In the case of Sapphire Canyon, researchers say that the minerals likely formed in low-temperature conditions, rather than in high-heat systems. That reduces the likelihood of purely abiotic processes. The obvious conclusion is that the spots were formed by microbial processes instead.

It should be noted, however, that the study doesn't claim direct proof of life on Mars. Instead, it highlights a combination of rock textures, chemistry, and mineral associations, which is best explained by processes that are linked to microbial metabolism on Earth. Sapphire Canyon thus makes Jezero Crater a top candidate when it comes to potential places that might have supported life on the Red Planet.

Discovering potential biosignatures on Mars is just a first step when it comes to finding signs of past Martian life. The more difficult challenge is proving whether they truly record traces of ancient life or are just a product of geochemistry. Ken Farley, a project scientist for the mission, warned that instruments like the Perseverance rover can't provide the level of certainty required for such a claim. According to him, the only way to know for sure is for NASA to find a way to bring these samples back to Earth for further study.

Bringing samples like Sapphire Canyon back to Earth would allow scientists to apply techniques far beyond the rover's capabilities. Laboratories would allow them to perform tests like isotopic analysis and nanoscale imaging. These methods would distinguish between microbial fingerprints and purely abiotic chemical reactions, and they can do so with a degree of precision impossible for Perseverance.

If we could confirm even just one of the rock's features as biological in origin, it would be the first direct evidence of extraterrestrial life. If not, the results would still reveal new details about Mars' geochemical past. Either outcome would be transformative for our understanding of the Red Planet. This is why the return of the Mars samples remains a central priority for NASA and its international partners.