Study reveals how to tell real alien life from chemical fakes

Scientists searching for extraterrestrial life have a problem: they can find the molecular fingerprints of biology everywhere. The issue is that fingerprints themselves are not unique. Life-building components like amino acids, proteins, and fatty acids can be created in non-living systems in just the same way they can be created by living things.

Phosphine presence in the Venusian atmosphere can point either to bacteria or to sulphuric acid reactions. The detection of dimethyl sulphide in the atmosphere of exoplanet K2-18b caused some hope, followed by doubt.

Fingerprint detection does not equal detection of life itself. It implies detection of a print that any person could have left there.

In recent studies carried out by scientists, including Gideon Yoffe of the Weizmann Institute and Fabian Klenner of the University of California, Riverside, there may now be a new technique to detect deeper fingerprint signatures in the search for life elsewhere.

Yoffe and Klenner adopted the idea from ecology, where life on earth is evaluated based on diversity and abundance. But their method uses this concept for molecules.

The research team analysed data from about 100 samples of asteroids, fossils, meteorites, microbes, soil, and synthetic material in the lab to examine how different amino and fatty acids are organised in biological and abiotic processes.

Amino acids produced by organisms were more diverse and more evenly distributed across a sample than those made abiotically. Fatty acids showed the inverse; they were less diverse and less evenly distributed when created by life.

"Our approach could help make the search for life more efficient," Klenner told Space.com. "If a molecular assemblage shows no life-like organisation, that may make it a lower priority target."

Neither pattern alone proves life exists, but the organisational signature does tell you something important: this wasn't random chemical activity.