Sumer version
Nibiru came very close to Tiamat, a planet several times larger than earth, and one of its many moon struck Tiamat, cleaving the planet in two. The Sumerians explained on their clay tablets, Tiamats rubble formed the asteroid belt and many comets. Its other half, now called Earth, was catapulted into its new (present) position. The moon was captured from Niburu. Many other consequences of the collision, including the origin of the iron core and the collisions effect on the orbits of other planets are explained.
Science version
"Our thinking of the early solar system as a plodding and predictable place [has given] way to the notion of planet-size objects careening into one another in wild, stochastic ways," writes Robin Canup, a fledgling planetary scientist at the Southwest Research Institute in Boulder, Colorado.
With this shift in thinking, even the old guard has rediscovered its enthusiasm. "It's fair to say the giant-impact theory has more truth in it than any other theory," says Melosh.
http://m.discovermagazine.com/2003/feb/featmoon
and
"Everything in the giant impact model is hot, hot, hot," he said. "It's incompatible with what we see in the geologic record. Earth is cool enough at that time to have ocean water on its surface."
Malcuit's computer modeling studies, which he has worked on since the 1980s, show that it is possible for Earth's gravitational pull to capture the moon.
At first, the moon's orbits would have been highly elliptical, swinging close to Earth and then far away about eight times a year.
The gravitational pull from each pass would have stretched the planet 18 to 20 kilometers (11.2 to 12.4 miles) near the equator, churning the hot mantle and crust. Rocks closer to the poles, like those found today in Australia, would have been spared. The upper layers of the newly-captured moon would have melted from gravitational friction, until the satellite's orbit stabilized about 3 billion years ago.
