🧬 Potentially biological carbon discovered on Mars

Did Mars once harbor life? NASA's Perseverance rover has just detected long carbon chains in two samples of Martian rock, a discovery that strengthens this possibility. Collected in Jezero Crater, these samples reveal the clearest traces of carbon ever observed on the red planet. Scientists believe these molecules could be the remnants of ancient microbial activity.

Carbon is the basic building block of life on Earth, and all living organisms are made of elaborate organic macromolecules. On our planet, this type of carbon is often found in very old rocks and sometimes serves as the only organic evidence of past microbial life. Researchers think that early Mars may have resembled Earth, which justifies the search for these molecules in ancient Martian rocks.


To detect these molecules, the rover's SHERLOC instrument used a laser to map the chemical composition of the rocks. The measurements revealed hundreds of organic carbon signals in two mudstones (sedimentary rocks), located in the Bright Angel region, on the edge of the ancient river valley Neretva Vallis. This is the first time such macromolecular carbon has been detected on the surface of a natural rock outside of Gale Crater.

The two mudstones studied show notable differences. In one, the carbon is mixed mainly with silicates, while in the other, it is associated with secondary carbonates and sulfates. The carbon in both rocks appears relatively intact, suggesting it may be resistant to radiation and oxidation, or that it was recently exposed on the Martian surface.

This discovery follows another striking observation by Perseverance: the rock named Cheyava Falls, which features characteristic "leopard spots." These markings can be created by high temperatures or acids, but also by the presence of life. Since none of these extreme conditions are known in the region, the biological hypothesis remains plausible, even if not proven.


The mudstones also display patterns reminiscent of those left by microscopic life on Earth, but these clues do not allow a distinction between a biological or non-biological origin. As Kyle Uckert points out, SHERLOC was not designed to distinguish between these two origins, but to identify promising rocks to bring back to Earth.

In the meantime, scientists continue to analyze the data. Confirming ancient life on Mars will require returning samples to Earth for further analysis. These results, published in Science Advances, add an important piece to the puzzle of Martian history.