It's been proposed in a new paper that it may be possible to detect life on exoplanets by examining the way their atmospheres vary slightly in composition. Gases like oxygen, carbon dioxide, and methane are expected to vary in their abundances in time with the seasons, as life's metabolism responds to varying temperatures, light levels, and moisture.

Spectroscopic measurements, taken over extended periods of time may be able to tease out these differences. Please find a link, below, with further information:


https://www.skyandtelescope.com/astronomy-news/astrobiology/identifying-life-from-varying-atmospheres/