Speculative Biochemistry: Because Earth is just one planet.

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kldickson
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Let's speculate!

For background, I am a neurobiology student. Ergo, I've got the requisite chem n' o-chem under my belt. (Would like to fit in some biochem, but I don't know if that's possible right now.)

From my own perousing of the material on the internet, it seems that carbon is really the only molecule we can do much of anything with, considering it's the easiest molecule to bond to 4 atoms stably and it's so freaking common. Silicon and phosphorus-nitrogen have been suggested, but neither system is stable enough to evolve life (because life always takes the easy way out; what that is is frequently beyond the comprehension of us idiot humans).

So - the anti-carbon-'chauvinism' movement is bunk. However, there's the question of chirality, and can carbon-based life require different sets of nutrients? Arsenic compounds, etc?

What characteristics can be regarded to be 'universal' as regards carbon-based life - i.e. there is no way we can presently think of that they can be contravened at all, barring something totally out of the blue?
 

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Whoops. I'll clarify what I said, then - I wanted to discuss what's been ruled out and what theories being tossed around definitively don't quite work.
 
kldickson said:
Let's speculate!

For background, I am a neurobiology student. Ergo, I've got the requisite chem n' o-chem under my belt. (Would like to fit in some biochem, but I don't know if that's possible right now.)

From my own perousing of the material on the internet, it seems that carbon is really the only molecule we can do much of anything with, considering it's the easiest molecule to bond to 4 atoms stably and it's so freaking common. Silicon and phosphorus-nitrogen have been suggested, but neither system is stable enough to evolve life (because life always takes the easy way out; what that is is frequently beyond the comprehension of us idiot humans).

So - the anti-carbon-'chauvinism' movement is bunk. However, there's the question of chirality, and can carbon-based life require different sets of nutrients? Arsenic compounds, etc?

What characteristics can be regarded to be 'universal' as regards carbon-based life - i.e. there is no way we can presently think of that they can be contravened at all, barring something totally out of the blue?

Plausibility argument instead?

Perhaps consider nitrogen fixation from interaction with magma; phosphorus chemistry leading to phosphates such as for polynucleotide bonds, and phospholipid membranes; mix with thermal gradients, purines, pyrimidines and amino acids, and enormous chemical time for nature to explore the space of endless possibilities. Might it not seem so implausible here and on Mars (has hematite oxidized iron; requires past oxygen atmosphere), as long as a magnetophere persists?
 
Zankaon, those molecules have carbon as a central element.