Scientists are increasingly convinced that organic molecules detected in Martian rocks are difficult to explain through non-biological processes alone, bolstering the possibility that life may have once existed on the red planet. A new study, building on the 2025 discovery of alkanes in ancient mudstones by NASA’s Curiosity rover, suggests that the original abundance of these molecules was far greater than previously thought and that purely geological explanations are falling short.
The findings, published in the journal Astrobiology on , don’t constitute proof of past life on Mars. However, they do indicate that the origin of these organic compounds warrants further, focused investigation. The alkanes, which could be fragments of long-chain fatty acids, are particularly intriguing because similar molecules on Earth are largely – though not exclusively – produced by living organisms.
The initial Curiosity sample revealed alkanes at concentrations of approximately 30 to 50 parts per billion. Researchers, led by Alexander Pavlov of NASA’s Goddard Space Flight Center, began by questioning whether these levels represented a depletion from a much higher original concentration. The Cumberland mudstone from which the sample was taken has been exposed to the harsh Martian surface, and its attendant radiation, for roughly 80 million years – a period sufficient to significantly degrade organic material.
To estimate the rate of degradation, the team leveraged laboratory experiments involving radiolysis – the breakdown of molecules through radiation. These experiments allowed them to model how quickly alkane precursors would decompose over time. The results pointed to a significantly higher original concentration, ranging from 120 to 7,700 parts per million (ppm) – a substantial increase compared to the current levels.
The researchers then systematically evaluated known non-biological sources of these organic molecules, including delivery via meteorites, atmospheric precipitation, and hydrothermal reactions. Even when considering all these potential sources in combination, they found that they couldn’t fully account for the estimated original abundance of alkanes. This discrepancy strengthens the hypothesis that biological processes may have played a role in their formation.
As detailed in a NASA press release, the study doesn’t definitively claim the discovery is evidence of life. Instead, it highlights the difficulty in explaining the observed organic compounds solely through abiotic (non-biological) means. The team emphasizes that unknown chemical processes or other unaccounted-for factors could also be at play. However, the findings underscore the importance of continued investigation into the organic molecules found within Martian rocks.
The organic compounds identified by Curiosity – decane, undecane, and dodecane – are hydrocarbons, consisting solely of carbon and hydrogen atoms. These are the largest organic molecules yet detected on Mars. While these molecules can be created through non-biological processes, their presence in such quantities raises compelling questions about their origin. The fact that they resemble fatty acids, which are fundamental building blocks of life on Earth, adds another layer of intrigue.
The study’s methodology involved a “rewind the clock” approach, combining laboratory radiation experiments, mathematical modeling, and data from Curiosity. This allowed researchers to estimate the original concentration of organic molecules before they were subjected to millions of years of radiation exposure. The discrepancy between the estimated original concentration and the amount detected today is what prompted the team to question purely geological explanations.
Scientists acknowledge that the possibility of unknown non-biological processes remains. However, the current evidence suggests that biological activity is a plausible, and increasingly compelling, explanation for the abundance of organic compounds discovered in the Martian mudstone. This discovery doesn’t resolve the question of life on Mars, but it does provide a significant new direction for future research and exploration. The search for definitive evidence of past or present life on Mars continues, with the latest findings adding a crucial piece to the puzzle.
The research builds on the initial discovery of alkanes in , and represents a significant step forward in understanding the potential for habitability on Mars. Further missions and more sophisticated analytical tools will be needed to definitively determine the origin of these organic molecules and to assess whether life ever existed on the red planet.
