[spindle]

Good question.

In astrobiology (and I think also in biology and most of chemistry) it means any molecules that contain carbon, with a few exceptions (exceptions include carbon dioxide and diamond - they don't count as organic). Strange definition, perhaps, but I'm certain that's what it means in astrobiology.

Organic molecules are not necessarily in living things and, indeed, interstellar dust clouds contain huge quantities of amino acids and other organic molecules which most astronomers believe have never been near a living thing.

[jameshart]

Be grateful these astronomers even made that distinction. They might have just said this stuff (or at least the parts of it that aren’t Hydrogen) was ‘metallic’ and left it at that.

https://en.wikipedia.org/wiki/Metallicity

Seems like asteroid astrophysicists like to be a bit more specific about this stuff than their stellar and galactic astrophysicist colleagues.

[spindle]

Yes!

Happily, it's become okay for them to talk about astrobiology. It was mostly taboo until a few years ago. (Just speculating here, but I think it was the discovery of lots of exoplanets that caused astrobiology to become permissible.)

[dylan604]

being technically right is good, but if you want funding, it has to be way more sexy sounding than that.

[jcranmer]

There's no terribly good definition of organic molecules in chemistry. The traditional definition is something that required a living organism to produce it, until inorganic synthesis of organic urea ruined that idea. The typical rule of thumb is an organic compound contains C-C and C-H bonds, but there's a whole host of exceptions to that rule (including urea, which lacks both C-C and C-H bonds).

The best I can come up with is that organic chemistry is the study of the interactions of a set of common structural motifs (called functional groups), and an organic molecule is something that contains those functional groups.

[10g1k]

Correct, this is the definition throughout all of biology, chemistry, and physics. Merely molecules with carbon atoms.