The Moon: Earth's Sneezeguard

Mandi Walls writes "SF Gate is running an article about looking on the moon for pieces of Earth that may have been knocked into space by collisions with asteroids, etc. The article claims the guys responsible for the idea came up with it while stuck in traffic. They were probably digging for change for a toll in the seats."

Comments

Isn't the moon itself a piece of the earth?

[T.Hobbes]

I had heard in SciAm awhile ago that the moon was created when a mars-sized asteroid hit a young (~4bn yrs), molten earth. This sent a v. large mass of rock into orbit which coalesced into what is now the moon.

In fact, after a little searching I found this at NASA:

How did the Moon come to be? The leading theory is that a Mars-sized body once hit Earth and the resulting debris (from both Earth and the impacting body) accumulated to form the Moon. Scientists believe that the Moon was formed approximately 4.5 billion years ago (the age of the oldest collected lunar rocks). When the Moon formed, its outer layers melted under very high temperatures, forming the lunar crust, probably from a global "magma ocean."

A few more links: Perty image and more detailed explanation; a google search on the topic.