[gus_massa]

> atp-powered

I think GTP-powered file is possible, even the glucose metabolism produce one GTP (and many ATP). (Perhaps I'm missing something, Chemistry is not my main specialty). Perhaps it is even possible to have NADH-powered life, but it is more different so it may be impossible.

> ossified calcium-braced

Diatoms use silica, insects have a protein exoskeleton, and octopus are weird.

> oxygen-absorbing, [...] protein-enriched, [...] water blobs

I guess these three are safe bets (with a little different selection of amino acids).

[madhadron]

Oxygen absorbing isn't necessary, of course. Life on earth got along without it for a while until those darned cyanobacteria starting poisoning everyone else.

[hansbo]

Eukaryote life did not appear until after the Oxygen Catastrophe though.

[madhadron]

That's true, but how much earlier might it have occurred if the oxygen catastrophe had not occurred and caused a mass extinction? Hard to say...