Re:Organic molecule compositions in samples of asteroid Ryugu
by ianai on Saturday February 25, 2023 @07:36PM
(#34941920)
For me, the ready abundance of AAs is plenty. If we saw a paucity of AAs outside earth then we could say we have evidence for the stuff for life being possibly unique to earth. That its presence seems to follow a knowable, significant rate suggests quite a lot of opportunities.
The 1:1 ratio of optical isomers is not consistent with life as we know it, suggesting an abiotic origin for the amino acids.
Amino acids are actually not very hard to make from simpler components. But quite harder to make enantiopure.
What's really hard to do is turn Acs into anything approaching the complexity we find in abundance in living systems.
It's enlightening to consider what evidence would be necessary to support a claim for the past or present presence of life. Clearly amino acids by themselves are not enough. And even enantiomerically enriched AA's could arise abiotically.
What you might look for is molecular complexity. One of the pioneers in the field, Leroy Cronin, developed a theoretical framework (Assembly Theory) that could be put into observational practice.
https://en.wikipedia.org/wiki/Assembly_theory
Cronin makes the analogy that if you found anything as complex as an iPhone on Mars, that would be pretty good evidence of the presence or at least influence of life at some point. It turns out you can do that at the molecular scale, but you need to come up with a way to define "complex."