Ninety-five percent. That is the accuracy rate at which a new chemical test, built around amino acid reactivity, correctly identified whether a sample came from something living or something that was not.
The method was developed by Christopher Carr at the Georgia Institute of Technology and his colleagues, and it works on a principle that separates living systems from inert chemistry in a precise, measurable way. In any non-living environment — a meteorite, lunar soil, a comet — reactive molecules tend to disappear. They get consumed by cosmic rays, or by other molecules around them. The most reactive compounds are the most vulnerable. Over time, without anything managing the process, they go first.
Life does the opposite. It holds onto reactive molecules because it needs them. The chemical processes that sustain living organisms demand reactivity, and so biological systems preferentially preserve what geology would destroy. That selective retention produces a statistical fingerprint.
Measuring the energy gap
To quantify reactivity, Carr and his team focused on a specific property of each molecule: the energy difference between its outermost electron and the next available space an additional electron would occupy during a reaction. A smaller gap means higher reactivity. The team calculated this value for 64 amino acids, including many that no organism on Earth uses.
Amino acids are the building blocks of proteins, and they appear across the solar system — in meteorites, in lunar samples — entirely without biology. Their mere presence, then, proves nothing. What the new approach measures is not presence but distribution. The team mapped the statistical spread of amino acid reactivities across more than 200 samples, drawn from abiotic sources like meteorites and moon soil, and from living sources like fungi and bacteria. From that distribution, they calculated the probability that any given sample came from life.
“The beauty of this approach is that it’s incredibly simple,” Carr says. “It’s highly explainable and it’s linked directly to physics.”
The underlying logic holds even for life that evolved elsewhere, according to the announcement. Carbon-based chemistry and the same electron-flow rules that govern life on Earth would likely apply to any living system in the universe. “Life inherently needs to control when, how and where molecules interact and reactions take place,” Carr says, “so that is going to involve having structures that can regulate the flow of electrons and how things interact electrically.”
Where it could go next
Henderson Cleaves at Howard University in Washington DC notes that using reactivity to detect life is not itself a new concept — but mapping it as a statistical distribution is. That distinction matters for how the test would be applied in practice.
The method could join a broader toolkit on a future mission to Mars or to Enceladus, one of Saturn’s moons and a long-standing candidate for extraterrestrial life. The instrument requirement is not trivial, though. Accurately measuring molecules and their relative abundances in the field is, as Cleaves points out, not straightforward.
The research is available on arXiv at DOI: 10.48550/arXiv.2602.18490.
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