theia's last dance

a minipost

We're less than a month away from the last North American total solar eclipse for a long time.  The Earth-Moon system is odd for a number of reasons.  How the Moon formed is still a puzzle, but evidence is getting much stronger and an odd fact about the inside of the Earth is partial evidence.

 

Here's the leading hypothesis:   About 4.5 billion years ago a Mars-sized planet struck the Earth resulting in the Earth-Moon system. There's been a lot of debate where Theia (one of the Titans and the mother of Selene, the goddess of the Moon) came from and how it hit the Earth, but one of the leading collision contenders has the event taking place in a few hours.   It can be argued we owe life as we know it to this event. 

More recent work links two huge structures inside the Earth to this event.