re: The evidence is not yet in. I don't see why not. I have predicted that microbial life will be found on Mars using the following reasoning:
If microbes could survive the event and the journey, they could be passed around via impacts.
Could Earth microbes hitch a ride in Earth rocks that have been blasted off the Earth, survive the journey, and find a niche on Mars?
Have any Earth microbes hitched a ride on our probes and survived on Mars? Despite sterilizing the probes, could some have survived. What about the USSR? Were their probes sterilized.
If we do find microbes on Mars, I’m betting they are related to Earth microbes.