Why ??
It would be reasonable evidence that over a very, very large period of time, under the right conditions, it is possible with even the smallest odds for the most basic living cell to form and then go through evolution over billions of years to form complex organisms and cells.
I think that's the unpopular hypothesis , majority still believe Life originated on earth but failed to give specific answer how, it will always come downs to ( something happen ) . Mars would have high radiation level than earth but some Organism survive in tougher conditions .
Even though if we find a rat size life form running on mars i would still have hard time believe it evolving into a intelligent life form like us Humans .
There are ideas about how it did actually. But we have never been able to experimentally prove it ever in simulated conditions. So it's, I don't know.