That they say it existed in the middle Hadean is striking. It was grabbing a toehold even when our world was a literal hellscape.
I think it increasingly likely that DNA first formed in space when the ambient temperature of the universe allowed liquid water. How else does a LUCA appear as if life on earth was a fait accompli, in the wake of a collision with another planet no less.
Edit: probably not
MMm… Probably not, at least in mechanism.
The issue is that of concentration. You need some kind of biogeochemical cycle that creates a concentration gradient. Otherwise the basic components are too diffuse to do anything meaningful.
I still lean into the “volitile ice balls” theory. NHx, NOx, Ox, etc. as volatile ices on asteroids in orbits where the iterate between freezing and melting. Moving between freezing and melting creates the biogeochemical cycle necessary to concentrate the basic elements sufficiently to be meaningful.
It was grabbing a toehold even when our world was a literal hellscape.
Actually this makes sense in the context of autocatalytic sets hypothesis - you’d need large variety of inorganic compounds and a strong energy gradient to kickstart a metabolism.
There’s great video on the subject from Sabine Hossenfelder https://www.youtube.com/watch?v=7yOiZLHDV3U
Part I’m talking about starts at 15:48
well, we need RNA before DNA. and we already have rna origin theories, so no, space dna doesn’t seem to fit there as an emergent property of rna to self replicate.
here’s a good one https://en.m.wikipedia.org/wiki/RNA_world
What do you mean liquid water in space? Liquid water doesn’t exist at low pressures, so you also need a somewhat pressurized environment like an atmosphere
I could be mistaken but I believe the hypothesis is that at one point the universe had an average temperature and matter distribution (pressure) to make it so that in most or at least a large portion of the universe it was significantly easier for organic molecules to start forming including the building blocks of DNA and then when it cooled/expanded some of that organic matter made its way to earth to eventually turn into life.
i don’t see how this could work, DNA degrades fairly quickly.
For those conditions you’re looking at a hilariously long time in the past, presumably closer to the big bang than now, and DNA can’t even last 100 million years.
Granted it probably lasts longer if frozen, but it’s not like things just stay frozen forever, and when we’re talking about thousands and thousands and thousands of years it seems incredibly difficult to believe that life would have started that way, especially compared to the relatively easy to imagine “water built up on an almost-molten earth, minerals leeched into it, and the heat caused chemical reactions that eventually ended up forming RNA or something”.
