Using NASA’s Curiosity rover, researchers analyzed pulverized rock samples and discovered the largest organic compounds ever detected on Mars. These compounds—decane, undecane, and dodecane—are hydrocarbon molecules with 10, 11, and 12 carbon atoms. They are believed to be fragments of fatty acids.
Most importantly, the discovery of these compounds on Mars suggests organic chemistry on Mars might have progressed to a level of complexity closer to what is required for life.
Scientists examined a rock sample in the Curiosity rover’s onboard lab, which is called Sample Analysis at Mars (SAM).
Fatty acids, produced by living things, help form cell membranes and perform various other functions. However, fatty acids can also be generated without life via chemical reactions triggered by multiple geological processes.
Although the molecules’ origin is uncertain, their discovery is thrilling for Curiosity’s team for several reasons.
Earlier, Curiosity scientists found small and simple organic molecules on Mars. However, discovering these larger compounds marks the first indication that Mars’ organic chemistry might have reached the complexity needed for life to begin.
NASA/Dan Gallagher
The study boosts hopes that large organic molecules, or “biosignatures”—which can only form in the presence of life—might be preserved on Mars. It eases worries about these compounds being destroyed by millions of years of radiation and oxidation.
This discovery strengthens the case for bringing Mars samples back to Earth, where advanced instruments can analyze them in greater detail.
Caroline Freissinet, the lead study author and research scientist at the French National Centre for Scientific Research in the Laboratory for Atmospheres and Space Observations in Guyancourt, France, said, “Our study proves that even today, by analyzing Mars samples, we could detect chemical signatures of past life, if it ever existed on Mars.”
In 2015, Freissinet and her team identified Martian organic molecules in the “Cumberland” sample—the same one used in this study. Curiosity drilled Cumberland in 2013 from Yellowknife Bay, an area resembling an ancient lakebed in Gale Crater, before heading to its main goal, Mount Sharp.
NASA/JPL-Caltech/MSSS
The detour paid off. Cumberland holds chemical clues to Gale Crater’s 3.7-billion-year history. It contains water-formed clay minerals, sulfur that preserves organic molecules, nitrates essential for life on Earth, and methane linked to biological processes.
Scientists concluded that Yellowknife Bay was once an ancient lake. This environment likely concentrated organic molecules and preserved them in mudstone, a fine-grained sedimentary rock. Evidence also suggests that liquid water existed in Gale Crater for millions—or possibly even longer—providing ample time for life-forming chemical processes to occur in these lake-like conditions on Mars.
These compounds were discovered unexpectedly during an experiment searching for amino acids in the Cumberland sample. Scientists heated the sample in SAM’s oven and found no amino acids, but they did detect small amounts of decane, undecane, and dodecane.
First ‘sun rays’ viewed on Mars
These compounds might have broken off from larger molecules during heating. By analyzing the results, scientists theorized that these molecules are remnants of fatty acids like undecanoic acid, dodecanoic acid, and tridecanoic acid.
The study revealed interesting details about the fatty acids in the Cumberland sample. Each fatty acid has a backbone of 11 to 13 carbon atoms, which is noteworthy because non-biological processes usually produce shorter fatty acids with fewer than 12 carbons.
Scientists think the sample might have even longer fatty acids, but SAM’s instruments aren’t designed to detect them. However, they acknowledge that instruments sent to Mars can only reveal so much, highlighting the need for further analysis on Earth.
Journal Reference
- Caroline Freissinet, Long-chain alkanes preserved in a Martian mudstone, Proceedings of the National Academy of Sciences (2025). DOI: 10.1073/pnas.2420580122
Source: Tech Explorist
