There are several different niches on earth where life exists in very hostile conditions. But that's not relevant to the question of life on Mars. The point is, did extremophile life arise spontaneously in such places, or did it migrate from somewhere else and gradually adapted to extreme conditions?
As far as we know, life may have a very low probability of appearing. We still don't know the exact combination of factors that led to the formation of the first living organisms, no one has ever been able to duplicate it in a laboratory.
The earth has several unique characteristics, one of them being its presence right in the middle of the habitable zone. However, the right temperature is not enough. The existence of a magnetic field is important, and plate tectonics may also be a fundamental factor, in its recycling of carbonaceous rocks that keeps the carbon dioxide in balance.
The presence of the moon could be fundamental to both the magnetic field and plate tectonics, due to the churning of the earth through tidal action. Also, ocean tides may have been a contributor to the creation of life, perhaps the concentration of soluble minerals in tidal pools were a factor. So, it could be that life will only evolve on a planet with a large moon.