I believe the asteroid belt was once a planet. What destroyed that?
The story goes that the asteroid belt and Earth were once a planet called Tiamat. In the creation story of the sumerians the Xth planet is called Marduk and it was sucked into our solar system by Jupiter and saturn as it plodded by. Marduk settled into its orbit - the eliptical 3600 yr orbit - as it was unable to escape the solar system.
During its first pass through the solar system it came to blows with Tiamat, the two planets traded moons until Tiamat was torn in half. Half of Tiamat became our asteroid belt, and half became the earth with Tiamats only surviving moon orbiting it. Earth was left with a pangea on one side and nothing on the other.
This theory nicely explains:
- The Asteroid belt.
- Why Earth had a pangea on one side and nothing on the other until Plate techtonics took over and evenly distributed the land masses.
- Why the moon is there.
- Also supposedley explains why certain planets have moons that orbit the wrong way.
- Why half of the surface of mars is missing. (Caught in the crossfire and aftermath I think).