Fatty Acids
Hydrocarbon-chain molecules with a carboxyl group; building blocks of cell membranes (as components of phospholipids) and important biosignature targets because they preserve well over geological time.
Astrobiology relevance
- Biological selectivity: Living systems produce a relatively narrow, structured distribution of fatty acids (typically even-numbered carbon chains, length-selective by enzyme class).
- Abiotic synthesis: Fischer-Tropsch-type and other prebiotic chemistries produce fatty acids with a broader, more evenly distributed range of chain lengths, including many that life does not use in quantity.
- Statistical-diversity biosignature (src-alien-biology-detection-method-2026-05): Yoffe & Klenner (2026) report that fatty-acid distributions show the inverse pattern from amino acids: abiotic pools are more even than biological ones. Used jointly with amino-acid statistics, this provides a discriminator.
- Mars organics-forward context: src-organics-forward-mars-life-search-2026-05 notes biology favors straight-chain C16/C18 carboxylic acids whereas abiotic synthesis yields highly branched aliphatic acids — another structural discriminator for a Martian biosignature.