[divbzero]

> "Our ultimate goal is the identification of life on a habitable exoplanet, which would transform our understanding of our place in the universe," concluded Madhusudhan.

What sort of observation or measurement would allow us to identify life on an exoplanet?

[gus_massa]

A lot of O2. As far as we know, the only source of a lot of O2 in the atmosphere are photosynthetic bacteria-like. So it will be a clear sign of life.

There are some more subtle cases, like the one discussed in this paper.