Viva de MoonJan 12, 2023
myrmepropagandist

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

Jan 12, 2023 at 3:03amWeb
Show threadjohncarneyauJan 12, 2023
@futurebird I love the whole Theia hypothesis 😍
Show threadElohiJan 12, 2023
@futurebird we made the moon. And everybody bad thought it was good y'all forgot the past.
Show threadViva de MoonJan 12, 2023
@futurebird Wow! My mind is blown. I learned something new today. Thank you! Gonna go read more about Theia.
Show threadAndrew Benedict-NelsonJan 12, 2023
@futurebird That would be quite a thing to see.
Show threadNicolas DufourJan 12, 2023
@futurebird Oh yes! It is super exciting for sure! so much geophysics left to do once over there for good!
Show threadMARGARET DJan 12, 2023
@futurebird I’m impressed that someone is even thinking about this. Sure beats the birdsite
Show threadSunnySideUpJan 12, 2023
@futurebird What makes anyone excited about science is a good thing
Show threadPacky AndersonJan 12, 2023
@futurebird I'd known about the collision hypothesis. What I didn't know was that the colliding object had a NAME.
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 threadMal 甄/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 🌼🌼🌼🏃🏿‍♀️🌼🌼🌼Jan 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 🌼🌼🌼🏃🏿‍♀️🌼🌼🌼Jan 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! ✔️

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...
Show threadSam AdamsJan 12, 2023
@berndandeweg The Moon's gravity could account for the lower density, couldn't it?
Show threadberndandewegJan 12, 2023
@Sameagle Theia would still have a higher density than Earth mantle in thar case. Isn't it?
Show threadSam AdamsJan 12, 2023
@berndandeweg I don't know. I think any meteorite has a higher density or it wouldn't survive the trip through our atmosphere, but I'm by no means an expert. My question about the density of the moon had more to do with material from Earth ejected into space and collecting around remains of Theia. Since smaller mass equates to lower gravity, I was asking whether that would cause a lower density of the material compacted around the core. I don't know the answer, but it seems logical to me.
Show threadGurre VildskäggJan 12, 2023
@berndandeweg @futurebird given that Earth and Theia was on similar enough orbits to in time strike eachother, would it not stand to reason that they both formed in very similar parts of the accretion disk around the sun and thus have similar compositions from that?
As a non-expert that would be my initial guess.
Show threadBarry GoldmanJan 12, 2023

@futurebird if you want to find Theia, there may be bits of her around. for instance in analyses like this, which i find fascinating

https://www.nature.com/articles/s41467-018-03808-6

there might be more updates on this particular analysis

A large planetary body inferred from diamond inclusions in a ureilite meteorite - Nature Communications

Ureilites are a type of meteorite that are believed to be derived from a parent body that was impacted in the early solar system. Here, the authors analyse inclusions within diamonds from a ureilite meteorite and find that they must have formed at above 20 GPa suggesting the parent body was Mercury- to Mars-sized.

Nature
Show threadCrysophylaxJan 12, 2023
@futurebird Sort of related is the possibility of meteorites that originated on the primordial Earth billions of years ago strewn on the Moon's surface.
Show threadTanoujin MilestoneJan 13, 2023
@futurebird what a nice rabbit hole. Learned about Lagrange spots today. Two bigger bodies almost sharing the same orbit, isn‘t that a bit exotic?
Show threadJames GarryJan 13, 2023

@tanoujin @futurebird

"Oh give me a focus,
Where the gravitons focus,
And the three-body problem is solved,
Where the microwaves play,
Down at three degrees 'kay',
And the cold-virus never evolved"

Chorus:
"Home, home on Lagrange..."
etc.

Show threadllewellyJan 13, 2023

@tanoujin @futurebird
my favorite bit of Lagrange nedery is DSCOVR, which stays near the sunward Sun-Earth Lagrange (L1) point, and (among other instruments) has a camera that takes regular pictures of the sun-facing side of the earth.

https://epic.gsfc.nasa.gov/?date=2023-01-11

sometimes the Moon passes between the Earth and DSCOVR, and you see this:

https://en.wikipedia.org/wiki/Deep_Space_Climate_Observatory#/media/File:Dscovrepicmoontransitfull.gif

EPIC :: DSCOVR

Daily natural color imagery of Earth from the EPIC camera onboard the DSCOVR spacecraft.

Show threadEmma Builds 🚀Jan 13, 2023

@futurebird

I saw a recent PBS Space Time about recent models of the collision where the Moon coalesced within hours (!!!) of the collision.

https://youtu.be/wnqPqV6DdFQ

The NEW SCIENCE of Moon Formation

YouTube
Show threadMichael W. ChoJan 13, 2023
@futurebird Is there any more fascinating astronomical event?