Read: J. F. Kasting, in Proceedings of NASA Ames Bluedot Workshop, D. Des Marais, ed., June, 1996.

"The exciting development in this field is that it now appears
feasible to look for Earth-sized planets around other stars using
a space-based, infrared interferometer and to examine their atmospheres spectroscopically. The practical way to search for life on extrasolar planets is to look for the 9.6-µm band of O3. O3
is a sensitive indicator of atmospheric O2, and O2 is, under most
circumstances, a strong indicator of photosynthetic life. Exceptions
to this rule include planets on either side of the HZ, as such planets
can conceivably accumulate large amounts of O2 abiotically. A
planet with O3 in its atmosphere and liquid water on its surface,
however, is very likely to be inhabited. The fact that we are on
the verge of being able to identify such planets suggests that
building such an instrument should be a top NASA priority."

Looking more like Mars was once a water world everyday and since there is traces of 03 left, who knows? Of course you do! You know everything right?

BD