Comment by jjk166
1 day ago
Note that the Bennu asteroid sample had approximately 5 nanomoles of nucleotides per gram, meaning 20,000 moles of nucleotides could be delivered by a single 4 million ton asteroid, which if it were a spherical carbonaceous chondrite would be about 183 meters in diameter. An asteroid about that size impacts earth roughly every 36,000 years, and that mass of meteor material falls to earth each century.
If primordial earth's oceans had nucleotide concentrations comparable to Bennu, then there would be about 10^39 nucleotides in the ocean.
I don't see any reason for the source molecules to come from space. We already know that nucleotides will spontaneously form and polymerize in conditions consistent with the early earth, and a meteorite origin just moves the source of those nucleotides elsewhere but doesn't answer how they formed.
Delivery by meteorites isn't necessarily the only or even primary source, but the fact is that it is a source we can directly observe, and it is a sufficient source. Earth's primordial chemistry likely did create more, but the existence of those conditions is theoretical, and such additional production need not be invoked to explain the needed level of abundance. Even a world with very different conditions from primordial Earth would likewise receive vast quantities of nucleotide during its formation and continuous replenishment afterwards.
space has been around for a lot longer than earth, its possible that inter planetary generation of nucleic acids may be primarily a matter of chemistry.
Nucleobase synthesis in interstellar ices[2019]
https://www.nature.com/articles/s41467-019-12404-1?error=ser...
Chemistry of Abiotic Nucleotide Synthesis[2020]
https://pubs.acs.org/doi/10.1021/acs.chemrev.9b00546
It's possible (proto-)life evolved in the pre-Earth protoplanetary disk.
If so, life might not require a special snowflake planet like Earth to develop. Development could be solar system-wide, and common in other early solar systems.
If raw materials isn’t the bottle neck for life every where, then what might it further down the line between oceans full of nucleotides and life? The oceans themselves?
Temperature range and magnetic field are my first thoughts.
I wonder how much nucleotides present in asteroids in space survive the massive heating in the atmosphere and the crash though.