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Comment by Insanity | Hacker News Reader

Whenever I hear people say they "look for earth-like planets" for life, because life can't exist on planets with conditions 'harmful to life'. (Such as extreme colds), I wonder _why_ they think so.

I'm not educated on the subject, but it seems to me that there's no good reason to think life can't exist in those places simply because we don't live in such a place.

(And, even on earth, there's microbial life in the oddest of places)

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Not really qualified to answer you, but I commonly read that it boils down to carbon being the base for life on earth, because that material can form complex bonds with so many other elements, without requiring much energy to do so. No other element seems to come close, though another contender is silicon. But if we assume carbon as the base component of other life, we also have to assume similar ranges of temperature etc. for it to thrive.

And from that liquid water is an essential part to all known life on earth. The temperature range needs to be similar to that of Earth for water to exist on the surface.

Silicon chemistry runs slower than carbon chemistry. There's more to it than just assuming carbon.

There's been a lot of work done on alternate biochemistries. Most of the alternate chemistries that look practical are at low temperatures, not high ones, because high temperatures inherently break down complex molecules.

See https://en.wikipedia.org/wiki/Hypothetical_types_of_biochemi..., or look up Cronin's work on metal-based self-replicating structures.

It's easier to look for conditions we already know can lead to life.

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