…I suspect that if that fungus actually exists there, it’s because it came along for the ride. And that ‘if’ is a big if. I don’t think we’d be able to really tell without sending somebody to actually look, preferably with a full biolab included.
PS: Yes, I’m assuming that the fungus would try to kill us. I don’t trust fungus in the slightest. Not on Earth, and definitely not any hypothetical Martian equivalent. I’ve seen zombie flicks. My kid played The Last of Us. I know how this ends.