Kelsey Preisel

by a giant impact with a Mars-sized body named Theia and Earth that then shot out magma from the Earth and that balled up and formed the moon.

Wow.

There's been other impacts throughout Earth's history that often coincide with mass extinctions.

And so when I was first learning about it, I was thinking of impacts are this crazy catastrophic thing that happens.

Little did I know they could form a brand new planetary body.

Whatever was going on back then has been recycled by plate tectonics, by erosion, but from our atmosphere, from our oceans.

We use the moon as this, you know,

archive of everything that has happened in the solar system.

And we've visited it and we've sampled it and we've been able to analyze those things in our lab, which is something we haven't done for any other planetary body.

This is a dichotomy that we've recognized for a really long time.

And with recent sample return missions from the Chinese Space Agency, we now have a sample from the far side to start to compare to the near side.