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 threadmyrmepropagandist
@berndandeweg I thought the impact theory was pretty much acceptedโ€ฆ or that at least itโ€™s the best of the known theories thus far?
Jan 12, 2023 at 12:05pmWeb
Show threadMal ็”„/kalessin/PeriJan 12, 2023
@futurebird @berndandeweg I also thought it was difficult to still explain the moon's stable orbit with the impact theory. That was why I thought it was accretion from similar material.
Show threadMihailik ๐ŸŒผ๐ŸŒผ๐ŸŒผ๐Ÿƒ๐Ÿฟโ€โ™€๏ธ๐ŸŒผ๐ŸŒผ๐ŸŒผJan 12, 2023

@perigee @futurebird @berndandeweg

This documentary is amazing, greatly entertaining and informative too.

https://youtu.be/Ghd8H-KvwVA

Catastrophe - Episode 1 - Birth of the Planet

YouTube
Show threadMihailik ๐ŸŒผ๐ŸŒผ๐ŸŒผ๐Ÿƒ๐Ÿฟโ€โ™€๏ธ๐ŸŒผ๐ŸŒผ๐ŸŒผJan 12, 2023

@perigee @futurebird @berndandeweg

Must be a bit outdated by now, but those models from 10y ago favoured the Moon accreted from hot liquid/vaporised rock halo.

That'd definitely give stable orbit (friction evens out kinetic anomalies).

And that would leave only very generic and faint traces of Theia. It's melted like Arnold.

Show threadChristopherJan 12, 2023
@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
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! โœ”๏ธ

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.
Show threadberndandewegJan 12, 2023
@futurebird i agree with the latter, but thay does not make it the only possibility...