NASA's Perseverance rover has discovered complex carbon compounds on Mars' surface that may indicate traces of ancient microbial life on the red planet.
The Bright Angel outcrop mudstones were found to contain organic carbon using the Sherloc device. This was carried out while the rover was in the Neretva Vallis, which was formerly a river that supplied water to the Jezero crater billions of years ago.
This type of carbon is known as macromolecular carbon, or MMC. Living things contain this carbon. But this substance may also be the result of geological processes over millions of years.

A specialist from Arizona's Planetary Science Institute informed a news outlet "It might come from biological sources like fossilized organic matter found in microbial mats and coal," according to The Guardian.This structure could also result from meteorites that have crashed nearby or from a chemical reaction between rocks and water.
2024 disclosures
Scientists and space fans turned their attention to the Bright Angel outcrop in 2024 after Perseverance identified nodules and patches on the rocks that seemed to resemble characteristics on Earth caused by fossilized bacteria.Former NASA acting head Sean Duffy said, "This very well could be the clearest sign of life that we've ever found on Mars," when information about the discovery was released in 2025.
Perseverance's latest discovery follows the Curiosity rover's same find. According to the researchers who published the findings in Science Advances, "these organic-bearing stones have now been located in the red planet about 2,000 miles apart, indicating that the habitability of Mars and the availability of organics may have been widespread throughout the planet billions of years ago."

Tests must be conducted on Earth
Regarding the study, Professor John Bridges, a planetary scientist at the University of Leicester, told The Guardian, "We can already see that Jezero was a habitable environment for any primitive life, with not just textures hinting at the possibility of life at Bright Angel but the relics of carbon building blocks that would be present if life had existed in this ancient delta."The cause of the intricate carbon structures cannot be determined by the rovers NASA deployed to Mars; only this can be done on Earth.

"The science payload of the Perseverance rover was not designed to distinguish between organics formed via abiotic and biotic processes but was instead chosen to identify compelling rocks to be collected for possible return to Earth for more rigorous testing," stated Dr. Kyle Uckert, one of the paper's co-authors. "The best way to determine the biogenicity of these rocks is to conduct these follow-up analyses on Earth."