Perseverance confirms complex organic carbon in ancient Mars rocks

The confirmation builds on NASA's September 2025 announcement that Perseverance had identified a potential biosignature. A potential biosignature is a substance or feature that could have formed through biological activity, although other explanations are possible. The new study, co-led by Ashley Murphy, a postdoctoral researcher at the Planetary Science Institute, and Kyle Uckert, deputy principal investigator of the SHERLOC instrument, provides what the researchers describe as definitive confirmation that the rocks contain organic carbon.

Billions of years ago, water flowed through a river channel into Jezero crater, carrying sediment that gradually settled on the bottom. Over time, those fine particles hardened into the mudstone formations Perseverance is exploring.

The measurements came from SHERLOC, an instrument on the rover's robotic arm that uses Raman spectroscopy and laser light to identify minerals and organic compounds without damaging rock. The team detected macromolecular carbon, a form of carbon made of large, interconnected networks of carbon atoms also found in rocks on Earth and in meteorites. It was found alongside carbonate and sulfate minerals that formed later as water altered the rocks, raising the possibility that organic material entered or formed during at least two separate periods of Martian geological history.

One of the most striking results is where the carbon was found: a few microns below the exposed surface, the shallowest detection of macromolecular carbon ever reported on Mars. Radiation, sunlight and chemically reactive substances on the Martian surface can break down organic molecules. Scientists would generally expect these conditions to make long-term preservation especially difficult so close to the surface. “The MMC detected in the Bright Angel mudstones is either resistant to degradation and/or has been sufficiently shielded by other minerals, such as clays, or iron-rich Martian soil,” Murphy said.

The findings also suggest organic carbon may not have been confined to a single region. Perseverance collected the Bright Angel sample more than 2,000 miles from Gale Crater, where NASA's Curiosity rover previously found organic compounds. “It is encouraging for Martian habitability,” Murphy said. “This indicates that billions of years ago, organics may have been more than just locally present and may have been more widely available in ancient lakes and rivers on Mars.”

“While the specific formation mechanism of the MMC detected in the Bright Angel mudstones remains unknown, this is still one of the most exciting findings to date,” she said. Determining whether the rocks contain fossilized microorganisms remains beyond the capabilities of the rovers now on Mars, which do not carry the large, energy-intensive laboratory equipment needed to conclusively distinguish fossil evidence from geological processes. Perseverance collected a sample from a rock named Cheyava Falls, and if samples from the Bright Angel formation eventually reach Earth, scientists hope that examining them in Earth laboratories could help reveal how the carbon formed and whether biological processes played a role. Murphy called the discovery a “resounding win for Mars science.”