A Weizmann Institute-led team has proposed a statistical biosignature strategy that distinguishes biotic from abiotic samples using relative abundance patterns within molecular families such as amino acids and fatty acids. The approach could offer a simpler alternative for planetary missions, where more familiar biosignatures such as chirality or isotope ratios are often difficult to measure and can be obscured by contamination, degradation, or geological overprinting.
Rather than focusing on individual compounds, the researchers looked for a broader statistical signal in how molecules are distributed within an assemblage. To do so, they adapted ecodiversity methods from ecology, treating each molecular profile as an assemblage and quantifying its richness and evenness using Hill numbers and evenness curves.
“Many current methods of searching for extraterrestrial life are limited because they require either complicated processing of organic material or highly specific analytical methods – work you currently cannot perform in outer space,” said lead author Gideon Yoffe in the team’s press release.
The approach was tested on a deliberately heterogeneous dataset of amino-acid profiles from terrestrial, extraterrestrial, and experimental sources, then extended to fatty acids. Uncertainty was propagated through the analysis, and pairwise dissimilarities were quantified statistically. “Our approach does not require fancy analytical instruments,” said co-author Yohai Kaspi. “It can be applied quite simply with any method capable of measuring relative abundances of different molecules, such as mass spectrometry.”
Across the amino-acid dataset, biotic samples were consistently more diverse than abiotic ones, despite wide variation in preservation history, extraction methods, and sample origin. Fatty acids showed the same overall separation, but with the opposite pattern: biological samples were less even, reflecting the narrower subset of chain lengths selected for membrane function.
The team also tested how well the signal might survive in harsher planetary settings. Simulations of radiolytic degradation in Europa-like near-surface ice suggested that the diversity signal can persist even as molecular profiles are progressively altered, supporting its potential use on samples with complicated exposure histories.
Because the framework relies on abundance structure rather than pristine molecular inventories, it may be better suited to the imperfect samples that missions to icy moons, asteroids, or Mars are likely to return. If so, the first evidence of alien life may emerge less as a clean chemical signature than as a pattern within a broader molecular assemblage.
“I’ve been fascinated since childhood with anything connected to the search for life beyond Earth,” added Yoffe. “To me, this kind of detection would be one of the most exciting scientific discoveries ever made.
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