Question #60f08

1 Answer
Nov 9, 2017

This is a fascinating question, and one that is still being actively considered. I can give you a basic answer here and point to better sources.

Explanation:

The moon almost certainly formed as a result of an enormous impact with a Mars-sized body very early in the history of the solar system. The date isn’t precisely known, but was about 100 million years after the Earth formed. The impacting body, often called Theia, probably struck a glancing blow, removing a large volume of crust and upper mantle from the Earth whilst leaving its core to fuse with ours.

The moon may then have formed very quickly from the debris and the impact has had huge consequences for Earth ever since. We have an unusually large core that produces much more heat than would be expected for a planet of our size. This gives rise to continental drift, which allows elements to be recycled and may have caused life to start on the planet.

It also gives rise to our magnetic field which protects us from the vast majority of high energy x-rays etc. emitted by the Sun (or pinging round the galaxy.)

We are very lucky to be a double planet, on a number of levels.

Suggested follow up:

A quick starter at https://www.space.com/19275-moon-formation.html

And a more authoritative discussion (in my opinion) at: https://en.m.wikipedia.org/wiki/Giant-impact_hypothesis