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The Sample Analysis at Mars instrument onboard NASA’s Curiosity rover has detected decane, undecane, and dodecane molecules in a sample from Gale crater.
This graphic shows the long-chain organic molecules decane, undecane, and dodecane, and NASA’s Curiosity rover. Image credit: NASA / Dan Gallagher.
“Curiosity’s primary scientific goal is to quantitatively assess the habitability potential of Mars, past or present,” said Dr. Caroline Freissinet, a researcher with CNRS and the Laboratoire Atmosphères et Observations Spatiales, and her colleagues.
“The Sample Analysis at Mars (SAM) instrument suite onboard the rover is devoted to this task by taking an inventory of the organic and inorganic compounds present at Mars’ near-surface as potential chemical biosignatures and exploring the nature of their preservation.”
Using the SAM instrument, the researchers analyzed molecules released from a drilled mudstone sample called Cumberland collected at Yellowknife Bay, a geologic formation in Gale crater.
They were able to detect three long-chain alkanes: decane (C10H22), undecane (C11H24), and dodecane (C12H26).
“These long carbon chains, containing up to 12 consecutive carbon atoms, could exhibit features similar to the fatty acids produced on Earth by biological activity,” the researchers said.
Dodecane represents the highest molecular mass organic molecule identified at the Martian surface to date.
“The detection of long-chain alkanes indicates a variety of sources of organics and preservation mechanisms in the Cumberland sample,” the scientists said.
“Clay and sulfate minerals are expected to play an important role in this long-term preservation.”
According the authors, the source of the Martian long-chain alkanes remains uncertain.
“Laboratory experiments support a source from the saturated form of straight-chain, primary carboxylic acids, i.e., undecanoic, dodecanoic, and tridecanoic acids for decane, undecane, and dodecane, respectively,” they said.
“Although abiotic processes can form these acids, they are considered universal products of biochemistry, terrestrial, and perhaps Martian.”
“Thus, the provenance and distribution of these molecules are of high interest in the search for potential biosignatures on Mars.”
The findings appear in the Proceedings of the National Academy of Sciences.
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Caroline Freissinet et al. 2025. Long-chain alkanes preserved in a Martian mudstone. PNAS 122 (13): e2420580122; doi: 10.1073/pnas.2420580122
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