Moon was Formed of Earth Fragments After Another Planet Smashed into Earth

The traditional theory that the Moon was formed out of fragments of Earth blasted into space after a massive planetary collision 4.5 billion years ago has gained support from two new studies. 



Previous theories have suggested that the Moon could have been made from pieces of another planet that crashed into Earth, but recent studies showing that Earth and the Moon have the same isotopic composition discount that idea. In fact, the Moon is of the same substance as the Earth.

Matija Cuk of SETI and Sarah Stewart of Harvard reckon the Moon was formed by the rapid spin of the ancient Earth. If its rotation rate at the time of interplanetary dust-up was significantly speedier, giving a "day" of just two to three hours, the planet would have thrown off the necessary material to form the Moon.

If the Earth was spinning through a day of just two hours, it would be near the point when it would start to fly apart itself from rotation forces, making it much easier to throw away loose bits of itself.