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Comment by lupusreal | Hacker News Reader

Abiogenic synthesis of "primordial soup" is fairly straight forward, see the Miller-Urey Experiment. A soup of random amino acids and whatnot might be created in a number of ways on Earth, so it's a stretch and not very interesting to suppose that such soups didn't exist on Earth and were brought in by space. The interesting panspermia hypothesis is that actual life came down from space. Finding amino acids in space could be evidence for that, but if the stuff found in space is mixed chirality that undermines those chemicals as evidence of life in space. Mixed chirality implies a mundane abiogenic origin.

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These findings show that biochemical compounds, once thought to be fragile and denaturate quickly in non-earth conditions, can apparently survive space conditions for a long time, even in universe metrics, so they could travel far. If they can, maybe cells can too. But that doesn‘t mean it‘s likely to find actual life on a random asteroid. Of course there is equal chirality in lifeless conditions. The ultimate question is: How did the first cell came to be? Everything after that seems explainable, if not predetermined. But that the first cell just randomly happened in the primordial soup - that looks extremely unlikely, yet it‘s the best explanation so far. If cells could travel on asteroids, it’s (equally? Less? Who could tell?) likely that the first cell just dropped here, intentionally or otherwise. Which would put the question of creation just to a different time and place. Somewhere in the universe, billions of years ago, life happened. Maybe it spread through the galaxy. Maybe sometimes a life carrying planet explodes, spreading asteroids with cells. Maybe some of them drop on planets with the right conditions. Given enough time, how unlikely is that as compared to random creation here?

> But that the first cell just randomly happened in the primordial soup - that looks extremely unlikely,

I don't understand this. Aren't cells just spherical structures that would form naturally from hydrophobic molecules suspended in water/tide pools? That seems likely to me, but I have no background in chemistry/biology.

Nick Lane argues in "The Vital Question" [0] that simple cell membranes are not enough for complex life and complex membranes may have evolved in matrixes around hydrothermal vents.

[0] https://en.wikipedia.org/wiki/The_Vital_Question

No! A cell is an incredibly complex machine and we have just begun to understand how it works! Admittedly, the wikipedia page for cells don‘t transfer that fact well (https://en.m.wikipedia.org/wiki/Cell_%28biology%29). I can‘t explain it all here, but yes, cells are essentially made of proteins and other organic compounds which have been found on that asteroid (and other asteroids before). But that is similar to the fact that a human is made of 14 chemical elements - it’s not telling you at all how the machine came to be and works. The Miller-Urey Experiment showed that those organic compounds could be created from anorganic material, which reversed the old belief that only organic matter can create organic compounds. But from there to a working, functional cell is still a long, looong way. Like, an aminoacid/ protein is a nail (and a plate, and a valve, and a million other components), a cell is a spaceship. That can harvest it’s environment and build new spaceships. Every living thing consists of cells, and we all go back to one first cell, that‘s the obvious conclusion when studying the system of life. But that first cell must have been incredibly complex, alone for the fact that it could take surrounding matter and build a new cell out of that.

There is an enormous amount of functional structure in even the simplest known cell. Cut down as much as possible, it's still billions of atoms.

Couldn’t there exist a chirality filter on earth?

The question is "how?" though. The chirality filter on Earth is basically Earth-life: it almost ubiquitously creates left-handed amino acids. But all known chemical ways of doing this produce racemic mixtures of both types.

If we found say, a high pressure synthesis method which was heavily biased chirally, then that would be good evidence but none has been discovered.

Is there any evidence of one or such a theory?

I am a total noob in chemistry and Claude said that it was a great question, but the answer were quite unclear about the feasibility. Mainly theoretical filters on lab scale. So that led me to put forward the thought.

Nobody has found or even so much as proposed a very good one. There's a bare handful of reactions that can tend to amplify chirality, but most uncontrolled chemistry (including things like Miller-Urey) produce a biologically-useless random high-entropy mix, and it is fairly unclear that these handful of reactions, which aren't even necessarily obviously useful ones and require some fairly special conditions, could possibly overwhelm the entropy of all the other reactions blasting out random combinations of things.

AFAIK there isn't even a known way to start with "normal chemicals" and produce highly-chiral reactions reliably in the lab. We get all our chiral molecules by extracting them from biology.

I think it should be possible to separate stereoisomers by crystallization, at least in some cases. You then have to sort through the crystals.

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