[throwup238]

Dude, just read the Wikipedia article: https://en.wikipedia.org/wiki/Hypothetical_types_of_biochemi...

It’s not impossible, but we’ve got a ton of evidence why it’s extremely unlikely. It’s a long list including stuff like possible quantum transition states enabling biochemistry, reactivity with oxygen (the third most abundant element), and spectroscopic transparency. It’s an active area of research that keeps coming up with dead ends.

Ammonia and methane are the best candidates but those would only be possible at low temperatures that preclude lots of other reactions.

[ceejayoz]

The Wikipedia article supports my point - plenty of smart folks think it's at least plausible for alternative chemistries to work.

An ammonia-based life form at our stage of exploration is probably gonna scoff at the idea of scaldingly hot liquid water as a basis for life, too.

> It’s an active area of research that keeps coming up with dead ends.

So's SETI so far, but I'm not willing to conclude extraterrestrial life is impossible just yet.

[throwup238]

And none of those smart people have come up with any experimental evidence that it’s actually possible. No equivalent to amino acids or nucleotides or saccharides or… the list goes on.

I’m not talking about SETI, I’m talking about basic chemistry experiments. There are tons of experiments that can spontaneously form amino acids and nucleotides, even way outside the parameters normally considered habitable.

[ceejayoz]

That's similarly true for carbon-based life; abiogenesis remains a hypothesis in search of concrete evidence.

[throwup238]

There is tons of concrete evidence, you’re just ignorant of it. Start with Stanley Miller’s seminal 1953 paper “Production of Amino Acids Under Possible Primitive Earth Conditions” and go from there. There’s been a lot of work on the topic since then, several of which have made it to the HN front page.

[ceejayoz]

I'm aware of the Miller-Urey experiment.

It's only one piece of the puzzle, and we're aided significantly in it by knowing what the results are supposed to look like.

[throwup238]

We absolutely know what it’s supposed to look like: monomers. Monomers that can form polymers.

The specific chemical details are irrelevant. We have no evidence of other monomers that could enable non-water based life.

[JumpCrisscross]

> ammonia-based life form at our stage of exploration is probably gonna scoff at the idea of scaldingly hot liquid water

Ammonia-based life exists within water habitable zones; Mars is within our Sun’s conservative habitable zone [1]. (Also, “ammonia boils at 98°C instead of –33°C” at “60 atm, for example, which is below the pressures available on Jupiter or Venus,” meaning “ammonia-based life need not necessarily be low-temperature” [2].)

One reason to suspect ammonia-based life is rarer than carbon-based life is the universe contains a fifth of the nitrogen that it does carbon [3]. (This is why silicon-based life is also almost written off.)

[1] https://en.m.wikipedia.org/wiki/Habitable_zone

[2] https://www.daviddarling.info/encyclopedia/A/ammonialife.htm...

[3] https://en.m.wikipedia.org/wiki/Abundance_of_the_chemical_el...