Your favorite exosolar system and mine – TRAPPIST-1 – has long been known to have a few plants in its Goldilocks zone where water can exist in liquid form. New analysis of data from the JWST’s scan of planet TRAPPIST-1e now shows that in addition to surface water (in the form of liquid water or ice), it also has some form of atmosphere, increasing the chances that it could possibly harbor life.
I don’t know if that is detectable, but having an atmosphere is a good sign since it means either there is a protective magnetosphere or the atmosphere is replenished as fast/faster than it is stripped away by solar wind.