The fact remains, life appears to have arisen on earth very early in its history. It also appears to thrive in a variety of habitats, many of them which would be considered toxic by those organisms flourishing in the others. It has also survived all sorts of geological, climatological and astronomical catastrophes over the last few billion years. This, plus the easy availability in the cosmos of the necessary chemical precursors, certainly suggests (although I concede it does not prove) that life is common in the universe. If it is a chance or random rare event, why does it seem to have happened on earth almost as soon as it cooled off?

I do agree that for a planet to remain stable and otherwise suitable for evolution to proceed for several billion years may indeed be a very infrequent scenario, but I don't think we really know enough now to answer that question satisfactorily. IMO, that life arises frequently in the cosmos is not an unreasonable assumption, although I concede it is an assumption. But again, IMO, it is an assumption that must be investigated in any way we can.

Unfortunately, the ubiquity and inevitability of life will be easier to prove than its extreme rarity or scarcity. All it takes is one other living world to prove the first, it will require many dead ones to even suggest the latter.