There are theories that see deep sea hydrothermal vents as possbile cradles of life, though there's not much places on Earth more extreme by our mammalian standards. But... see them as the places with abundance of water, all-the-chemistry-you-can-eat *), free energy, shielded from radiation, storms, space debris and as stable in all its "extremity" as can be. *) "you" means "wildly complicated self replicating molecule" BTW, I sincerely recommend Rifters trilogy by Peter Watts, that starts near Juan da Fuca rift by one of such vents. SF so hard it comes with bibliography, mentioning "A hydrothermally precipitated catalytic iron sulphide membrane as a first step towards life", by M.J. Russel et al. (Journal of Molecular Evolution, v39, 1994) among others.