A new study suggests a biosignature [washington.edu] that the James Webb Space Telescope could search for:
The new study looks at the history of life on Earth, the one inhabited planet we know, to find times where the planet’s atmosphere contained a mixture of gases that are out of equilibrium and could exist only in the presence of living organisms — anything from pond scum to giant redwoods. In fact, life’s ability to make large amounts of oxygen has only occurred in the past one-eighth of Earth’s history.
By taking a longer view, the researchers identified a new combination of gases that would provide evidence of life: methane plus carbon dioxide, minus carbon monoxide.
“We need to look for fairly abundant methane and carbon dioxide on a world that has liquid water at its surface, and find an absence of carbon monoxide,” said co-author David Catling [uw.edu], a UW professor of Earth and space sciences. “Our study shows that this combination would be a compelling sign of life. What’s exciting is that our suggestion is doable, and may lead to the historic discovery of an extraterrestrial biosphere in the not-too-distant future.”
Also at Popular Mechanics [popularmechanics.com].
Disequilibrium biosignatures over Earth history and implications for detecting exoplanet life [sciencemag.org] (open, DOI: 10.1126/sciadv.aao5747) (DX [doi.org])