[nervousvarun]

Just curious how can anyone conclusively claim life arose only once? Don't they just say we only have evidence that it arose once?

Maybe it started twice or 100M times but 100% of those times the newly started life was "consumed" in some way by already existing life etc.

[mirimir]

Yes, that seems a dubious claim. There's no way to know, except though simulations, how many dead ends there were. What we know is that all existing organisms share basic biochemical features. More or less the same nucleic acids, amino acids, and so on. So other paths arguably got competed out. Or merged, as we know for nuclei, mitochondria and chloroplasts in eukaryotes. Probably also components of bacteria. Flagella, maybe? The whole DNA/RNA/protein thing could well be a kludge.

The especially cool aspect of searching for life elsewhere in the solar system is the possibility that we'll find other variants that dominated.

[jobigoud]

It's also because we have tried all sorts of approaches for the past 70 years or so and we haven't been able to bootstrap it ourselves.

[mirimir]

I doubt that any of the experiments have run for longer than a few years. And probably less.