[jerf]

I have never seen a convincing basis for life that isn't carbon. The next best candidate is silicon, but it seems like the problems are unlikely to be overcome.

Non-water may be just about possible: https://en.wikipedia.org/wiki/Hypothetical_types_of_biochemi... Non-water solvents may run at somewhat different temperatures.

However, strongly showing that an alternative is possible is a super, super uphill battle. If we weren't made of carbon and water, I'm not sure we could conclusively show that life could be built on it. But we probably couldn't disprove it. Ammonia is probably at least in the "not disproved" category. But I think most everything else is. If you seriously think about it, beyond the "my mind is so open it's falling right out", it's a pretty tall bar to find an alternative. (If you don't think so, spend some more time with organic chemistry, and consider why we call it that. There is a reason life is based on it, and there's a reason we cleave the entire chemistry world into two pieces along that division.)

It is also in my opinion not that interesting a question ultimately. The big jump is the one from zero possible life substrates to one. Having a second one doesn't really change much, e.g., I don't see any compelling reason to believe there would be an "ammonia solvent" view of the universe versus a "water solvent" view of the universe or something.