A martian rock has lots of carbon on it, and it's not clear why

The material found on Martian rocks, Murphy’s team warns, might have originated from non-biological processes as well. A result like this usually invites two major questions, and the team immediately got busy trying to answer them. The first concern was that the signal could have been light bouncing off SHERLOC’s own fused-silica front window. Bright Angel was the first site SHERLOC examined after a dust-cover anomaly disabled its focusing mechanism, forcing the team to adopt a new operating mode. To characterize the new mode, Kyle Uckert, SHERLOC’s deputy principal investigator at NASA’s JPL, and his colleagues collected spectra from spare flight optics in their own lab. They also pointed SHERLOC at nothing in particular on Mars and at known calibration targets. All these were used to confirm that SHERLOC was working properly. The final confirmation of the data came when the team pointed it at Steamboat Mountain. “Other rock targets nearby do not exhibit the G-band spectral signal,” Uckert said. The Bright Angel signal was not coming from hardware. Murphy sees that split as evidence for at least two separate windows in which carbon could have been locked into these rocks. First, as organic matter settled into mud at the bottom of an ancient lake and was buried alongside the sediment and again when groundwater later moved through this buried rock and left behind new carbonate and sulfate minerals. In the end, though, the question of whether Bright Angel carbon is a remnant of ancient Martian life will remain open for quite a while. “The science payload of the Perseverance rover was not designed to distinguish between abiotic and biotic processes but to identify compelling rocks to be collected for possible return to Earth,” says Uckert. “Perseverance rover has an incredible instrument payload, but those instruments pale in comparison to world-class techniques that could be used to analyze these samples when they get back to Earth,” said Kevin P. Hand, the Perseverance principal investigator at JPL. Hand is especially interested in the isotopic signature of Bright Angle’s carbon, which might provide some indications of life. Another thing he wants to look into is chirality—a preference for one type of molecular handedness over another that is strongly associated with biotic origin. “We could also use some of the most powerful microscopes on Earth to search for ancient microbial fossils, if you will, that could be indicative of past life on Mars,” Hand explained. There is no shortage of abiotic mechanisms that could create such a material. Fluid-rock reactions in some environments are known to synthesize organic compounds with no life involved. Murphy notes that carbon found near carbonate minerals on Earth can be traced back to either water-rock chemistry or microbes, depending on the setting. Hand, though, hopes Perseverance still has a lot to discover on Mars before we ship the samples it has collected to Earth. “Now we are exploring the region outside of Jezero crater—the rocks over which we’re currently roving are perhaps some of the oldest rocks ever investigated by a rover on Mars,” Hand said. “There’s a chance that if life arose early on in the history of Mars, we might find some hints of it in the rocks we’re looking at now,” he added. Science Advances, 2026. DOI: 10.1126/sciadv.adx0047