Ok, with my microbiologist hat on: there's pretty strong molecular evidence that the earliest cellular lifeform on Earth (often called the 'progenote' or 'universal common ancestor') was an extreme thermophile. Obviously we only have sequence data from extant lifeforms (their ancestors...) to work with, but it looks like life adapted to less extreme environments, rather than the other way around. Taxonomically, many 'modern' extremophiles lie on branches of the 'tree of life' which diverged closest to the base of the trunk. That's why the microbial communities found around Earth's oceanic volcanic vents (which live without oxygen, using chemical energy, and independently of sunlight) are so interesting.
Going to Europa to look under the ice there should be at the top of NASA's wishlist, imho. That round of golf on Mars can wait...
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Ok, with my microbiologist hat on: there's pretty strong molecular evidence that the earliest cellular lifeform on Earth (often called the 'progenote' or 'universal common ancestor') was an extreme thermophile. Obviously we only have sequence data from extant lifeforms (their ancestors...) to work with, but it looks like life adapted to less extreme environments, rather than the other way around. Taxonomically, many 'modern' extremophiles lie on branches of the 'tree of life' which diverged closest to the base of the trunk. That's why the microbial communities found around Earth's oceanic volcanic vents (which live without oxygen, using chemical energy, and independently of sunlight) are so interesting. Going to Europa to look under the ice there should be at the top of NASA's wishlist, imho. That round of golf on Mars can wait...