TRAPPIST-1 and its seven interesting planets may be the most compelling stellar system we’re investigating, given the range of worlds here and the possibilities for analyzing an entire, nearby planetary system. But as we look toward examining systems like this with new space- and ground-based instruments, we may run into problems with searching for biosignatures. Both the TRAPPIST-1 planets and the promising Proxima Centauri b may be tough to characterize.
The problem: When searching for biosignatures, we’re looking for signs of metabolism, gases that are continually produced and remain out of balance in a planetary atmosphere. Ozone is one piece of the puzzle, one that signifies oxygen. Finding the latter in the same atmosphere with methane would be a compelling biosignature. But ozone could be hard to detect.
Ludmila Carone (Max Planck Institute for Astronomy) and colleagues now find that atmospheric circulation in planets close enough to red dwarfs to be in their habitable zone may mask the very signs we’re looking for. Ozone may become undetectable, trapped in equatorial regions.
The issue involves atmospheric flows, which will likely differ from what we see on Earth. The ozone in our stratosphere is formed when ultraviolet light from the Sun ...