biosignature

noun

bio·sig·na·ture ¦bī-(ˌ)ō-¦sig-nə-ˌchu̇r+

plural biosignatures

: something (such as a chemical compound, isotope, or cellular component) that indicates or suggests the presence of a biological process indicative of life

This will help astronomers learn to recognize "biosignatures"—clues that a planet's atmosphere has been influenced by life.—

Karen Schmidt, New Scientist, 2 July 2005

… the potential of the microbes to become fossils and serve as "biosignatures" for researchers seeking signs of early life in the remnants of ancient volcanism and hydrothermal activity on Earth—and, particularly, on Mars.—

David Perlman, San Francisco Chronicle, 21 Apr. 2005