the.com/biosignature
a chemical fingerprint left by something that was, or is, alive.
means any substance, pattern, or gas ratio in rock, ice, or atmosphere that strongly suggests biological activity produced it.
from coined in astrobiology circles as scientists needed a word for evidence of life that doesn't require finding an actual organism, borrowing 'signature' from forensics: not the criminal, just the fingerprint.
oxygen problemoxygen alone can form abiotically, so context matters
phosphine debatevenus clouds sparked a biosignature controversy in 2020
false positivesgeology can fake biology disturbingly well
james webb huntstelescope now scans exoplanet atmospheres for these clues