re: Hmmm
If there were such things on the Martian surface, craters with white rock deposits are possible sites to keep watch on.
The origin of the white rock deposits is still mysterious; one idea is that they may result from fluid material deposited at the surface from below, or they may have formed from beneath a heavy overburden (there are white rock like deposits more than a kilometer below the present surface in Valles Marineris and elsewhere.)
Still I don't see anything that looks like fumaroles here:
The small circular light spots look more like uneroded sections of white rock material. I don't see any smoke or other venting at all.
Cheers, BRFelix