Why does the Moon fall back to Earth at the end of the simulation?

From the article:

> During Earth’s earliest days, it was covered by a sheet of molten silicate rock. Dr. Hosono’s team wondered what would have happened if Theia had crashed into Earth at that time, rather than during a later, cooler, more solid phase.

This is the simulation of how a moon could have been formed, this is not supposed to represent the formation of the actual Moon.

> This is the simulation of how a moon could have been formed

The animation doesn't show a moon in a stable orbit forming, so obviously it doesn't even show how it could have happened.

Also, if you play the animation slowly, you can see a brighter circle forming at the point of impact, before the impact. Is that part of the simulation or an artifact of the animation, I wonder?

My interpretation is that the surface magma, cooled down hence the dull orange, is blown away by the bow shock in the atmosphere from the other body entering the atmosphere. This exposes the hotter, brighter, underlying magma.

Could of course be entirely wrong.

Wouldn't that require an unreasonably thick atmosphere? Our current atmosphere is only around 10 miles high. (Obviously, it all depends on what you consider as your cutoff.)

Possibly, I'm no expert.

I didn't think about timescale though, the bow shock would require very short timescale (if at all plausible like you said).

If it happens on longer timescales, then maybe it's just surface heating from the emission of the other body.

Gravity that attract mater imho (and make hot matter go on surface). There is another effect : the incoming moon is not a sphere any more before impact.

I'm guessing it's the low energy light from the rendered sphere.

A question I’ve been wondering about: To what extent is the contemporary Earth’s crustal composition a mix of Theia and the proto-Earth? If Theia was roughly one tenth of Earth by volume, where did all that matter end up?

This model puts the composition of the moon at around a 70:30 mix of Earth to Theia. This doesn't square with titanium composition of the moon rocks that indicate that the moon was formed from cooled earth materials.

https://www.wired.com/2012/03/moon-formation-collision/

I wonder how much bigger the Earth would have been if it hadn't been smashed by a planetesimal? (Assuming the theory is true).

Presumably Earth would be smaller without the impact. Mars-sized matter was added to the Earth as a result of the impact and all that was lost was the moon (and perhaps some smaller amount that escaped entirely).

Without tides we may not even exist in that scenario.

Reading about things like this (matter ejected from Earth into space) + recent research on extremophiles makes wonder if panspermia might be an accurate theory:

https://en.wikipedia.org/wiki/Panspermia

According to Neal deGrasse Tyson (source: his recent books and I think I've heard it on his YT channel too) it is quite possible that early Mars had better conditions for life than early Earth and that life could travel to Earth from there.

They should also account for the possibility that the moon rocks are actually from earth. Just in case the moon landing was faked