A fatty acid might be among organic molecules discovered on Mars by Nasa's Curiosity rover.
However, it's not possible at this stage to determine whether the compound has a biological or non-biological origin.
And contamination could still be responsible for the finding.
The results come from Curiosity's SAM instrument, and were presented at the 46th Lunar and Planetary Science Conference (LPSC) in Texas.
Nasa scientist Daniel Glavin described the results from the first "wet chemistry" experiment carried out by Curiosity.
A long-chain carboxylic acid, or fatty acid, was a good fit for one of the data peaks detected in a mudstone called Cumberland, he told an audience at the meeting. A form of alcohol molecule may also be among the compounds analysed.
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