Comment by andrewflnr

Moss requires quite a bit of liquid water to actually reproduce, since (IIRC) their sperm need to swim around to mate. So we're left with, like, maybe Europa, if there's enough light and enough water gets into the surface via cracks? I doubt there's enough light under the surface, even if you found a moss species that can survive being totally submerged in whatever saltwater hellscape is under there. Basically there are still going to be huge problems for moss anywhere besides Earth. They already mostly stick to wet environments here.