NASA's Perseverance rover has uncovered the most extensive evidence yet of complex organic molecules on Mars, detecting macromolecular carbon in rocks from the Bright Angel formation in Jezero Crater. The discovery, confirmed by an international team of scientists using the rover's Raman spectrometer, provides strong indications that organic matter—a key building block for life—was once widespread on the Martian surface. The findings were published last week in the journal Science Advances.
The organic material, known as macromolecular carbon (MMC), was found in two rock samples collected from the Bright Angel formation, an ancient riverbed that once flowed into the now-dry lakebed of Jezero Crater. The geological history of the area suggests that the organic deposits may have formed during two or more events billions of years ago, when water and sediments were carried into the crater. Fine-grained sediments settled and hardened into clay rocks, which the rover later analyzed. The MMC was detected in association with these fine sediments, as well as with carbonate and sulfate minerals that formed later during aqueous alteration.
Researchers emphasize that it remains extremely difficult to determine whether the carbon is of biological origin. Teresa Fornaro, a researcher at the Italian National Institute for Astrophysics (INAF) and a co-author of the study, noted that both biotic and abiotic materials, exposed to Mars' harsh conditions for billions of years, can transform into this type of complex organic matter. However, the presence of organic matter alongside mineralogical evidence—such as leopard spots that on Earth often result from biological processes—in a rock formed in a habitable aqueous environment could represent multiple lines of evidence for biogenicity.
Ashley Murphy, a co-author of the study and researcher at the Planetary Science Institute, described the discovery as one of the most exciting so far, even though the specific formation mechanism of the MMC remains unknown. One particularly striking aspect is the shallow depth at which the organic molecules were found: just a few microns below the Martian surface, thinner than a sheet of paper. This marks the shallowest detection of MMC ever achieved on Mars. The fact that complex organic molecules were identified so close to the surface, in an environment known for destructive solar radiation and chemical oxidants, is noteworthy.
Murphy explained that the MMC detected in the Bright Angel clay rocks appears to be resistant to degradation or was sufficiently protected by other minerals, such as clays or iron-rich Martian soil. The sample was collected more than 3,000 kilometers away from previous organic detections made by NASA's Curiosity rover in Gale Crater. This distance is encouraging for the habitability of Mars, Murphy said, indicating that billions of years ago organic substances may have been present not just locally but more widely distributed across ancient Martian lakes and rivers.
The Perseverance rover continues to explore Jezero Crater, collecting samples that could eventually be returned to Earth by future missions. The detection of complex organic matter in multiple locations strengthens the case that Mars once had the chemical ingredients necessary for life, even if the question of whether life ever existed there remains unanswered.
