An often repeated statement about any extraterrestrial object is: “if it has liquid water it might suport life”. On this assumption a lot of space probes, robots and rovers include the sensors and the instruments the search for traces of past life. This has had high priority in many missions to Mars and it will have high priority also in future missions to the satellites of Jupiter.
Now the thought came to my mind that the ability to support life might not be enough. Life on Earth exists in the most inhospitable places, even in lakes that formed below the polar caps. But the theory is that life evolved in the primordial soup, which was a very favourable environment, only later it spread to inhospitable environments.
To repeat myself, what I am saying is that the ability to support life and the ability to support the birth of life might be two different things. How much different is the question. If the answer is that the difference is strong and life needs a cosy environment in order to arise the assumption it had liquid water therefore it might have had life is moot.
So, how strong is the difference? Is just some liquid water in unknown conditions enough to let life arise, even if it might support existing life?
I’m not a scientist, but I think the question you’re asking is the question they’re seeking to answer by searching for life in these places. There isn’t an assumption that if it had liquid water it may have had life (that statement alone inherently isn’t an assumption), they are searching for any evidence of life on Mars because A) it’s the closest and easiest planet to get to and B) while we know in what conditions life on Earth arose, we can’t be sure the same conditions are necessary somewhere else, for life that possibly may not be carbon based.
We don’t know the conditions that life arose in on Earth. There are multiple hypotheses, but there is no conclusive evidence, and we certainly cannot reproduce life from the building blocks yet.
Yes, but, given that most of the fossils of archaic life was found where the primordial soup might have been present, that for the moment is the hypothesis with better support.
Though odds are highest for carbon-based, simple from it’s abundance.
Trouble is that between science and what we get from the media there is a big difference. In science the assumption is not there. But when you see the media reports about Mars or the future planned missions to Europa the assumption is there, blunt and with no attempts to justify it.