myrmepropagandistJan 12, 2023

The moon formed when Theia hit the earth. The surface of the moon is mostly material from the #earth with the same isotopes... but if we could drill into the moon... we could find some of #Theia according to some models of the collision.

Theia is still here! Just covered in a super thick earthy sweater.

I don't know why I find this so exciting-- it's probably not going to be anything shocking...

I guess Theia always seemed... vanished into the deep past. But Theia remains. #musings #moon

Show threadberndandewegJan 12, 2023
@futurebird but it remains a mystery still why the moon in chemistry and isotopes resembles so much our mantle. If you want to cover Theia with earth material, the moon should be more dense than it is. So the only possibility is that Theia (if it existed) should have had nearly the same composition as Earth.
Show threadmyrmepropagandistJan 12, 2023
@berndandeweg I thought the impact theory was pretty much accepted… or that at least it’s the best of the known theories thus far?
Show threadChristopher
@futurebird
Impact theory is widely accepted. Neither co-accretion nor capture do a good job of explaining the Moon's internal structure, not the high angular momentum of the Earth-Moon system.

It's still difficult to explain the degree of similarity in composition, though. People who study the hypothesis are always making new collision models to explore the possibility space.

One of them, from a new years ago now, even kind of explains some structures deep in the Earth's mantle.
@berndandeweg
Jan 12, 2023 at 12:48pmWeb
Show threadmike bayer  Jan 12, 2023

@kichae @futurebird @berndandeweg maybe one larger planet did split into two. Then after some period of orbital machinations, they collided!

I thought this thread could use an idea from a total ignoramus on the subject (don't they all!), so you can check off the box on that! ✔️

Show threadberndandewegJan 12, 2023
@zzzeek @kichae @futurebird well, sort of. There could have been a runaway geo nuclear reaction at the core mantle boundary (the D" layer) where supposedly mantle plumes are generated still.