NASA finds signs of possible ancient microbial life on Mars

What happened?

NASA's Perseverance rover has identified complex organic carbon, known as macromolecular carbon (MMC), in sedimentary rocks of the Bright Angel outcrop, located in Mars' Jezero Crater. The measurements were made by the SHERLOC instrument (Scanning Habitable Environments with Raman & Luminescence for Organics and Chemicals) and published in the journal Science Advances. This finding adds to previous detections by the Curiosity rover in Gale Crater, more than 3,200 km away, suggesting that organic matter may have been widespread across the planet billions of years ago. According to the study, the Bright Angel rocks are ancient mudstones that formed in a river delta, an environment that on Earth is conducive to preserving microbial fossils.

Why is it important?

MMC can form through biological processes (such as fossilized remains of microorganisms) or abiotic ones (reactions between rocks and water, or meteorite impacts). The presence of this compound in two such distant locations indicates that conditions for life may have been common on ancient Mars. Sean Duffy, former acting NASA administrator, called the finding "the clearest sign of life we've ever found on Mars," though scientists emphasize that more evidence is needed. Dr. Ashley Murphy of the Planetary Science Institute in Arizona noted that MMC can originate from biological sources such as fossilized organic matter in microbial mats and coal, but can also form from reactions between rocks and water or arrive in carbonaceous meteorites. This finding is crucial because it expands the known distribution of organic matter on Mars, suggesting that the processes that generated or preserved it were global.

Historical context

Since the Viking mission in the 1970s, the search for life on Mars has been a central goal. Viking's results were ambiguous: although they detected simple organic compounds, they failed to confirm biological activity. The discovery of organic molecules by Curiosity in 2014 had already opened the door to the possibility of past life, finding traces of methane and chlorinated compounds in Gale Crater. Now, Perseverance adds a key piece: the detection of MMC in a river delta, an environment that on Earth is rich in microbial fossils. In 2024, the Bright Angel rocks caused a stir when surface spots and nodules were observed that resemble structures produced by fossilized microbes on Earth. This new study provides the chemical composition of those rocks, strengthening the hypothesis of a biological origin, though not confirming it.

Consequences and next steps

This finding reinforces the need to bring Martian samples to Earth for more detailed analysis. NASA and ESA's Mars Sample Return mission aims to collect and send samples from Jezero Crater in the next decade, possibly by 2033. If a biological origin is confirmed, it would be the first discovery of extraterrestrial life. Meanwhile, Perseverance will continue exploring Bright Angel for more clues, and the rover is also expected to collect additional samples at the crater rim. Scientists plan to use isotopic and radiometric dating techniques on samples brought to Earth to determine whether the organic carbon comes from living organisms. Additionally, the study suggests that the presence of MMC in two craters separated by thousands of kilometers implies that organic matter may have been common on ancient Mars, increasing the chances that signs of life are preserved in other regions of the planet.

"This could be the clearest sign of life we've found on Mars" — Sean Duffy, former acting NASA administrator.

What readers should know

• The detected organic carbon is not definitive proof of life; it may have a geological origin or have arrived in meteorites.
• This is the first time MMC has been found in two such distant areas on Mars, suggesting a global distribution of organic matter.
• Confirmation will require analysis of samples in terrestrial laboratories, which will not happen until at least 2030.
• The discovery increases the likelihood that Mars once harbored microbial life, but it is not yet conclusive.
• The SHERLOC instrument uses Raman spectroscopy and fluorescence to identify organic compounds and minerals, providing complementary data to Curiosity's.

Speculations and warnings

Some media outlets have suggested that the finding amounts to confirmation of past life, which is incorrect. The scientific community insists that more data is needed. MMC can also be generated by geological processes, such as serpentinization (reaction of ultramafic rocks with water) or impact of carbonaceous meteorites. Additionally, the possibility of terrestrial contamination must always be considered, though rovers are designed to minimize it. The study authors emphasize that isotopic analyses of carbon and nitrogen, as well as identification of specific biomarkers, are required to determine the origin. Meanwhile, the finding is an exciting step, but not definitive, in the search for life on Mars.