An ancient planet named Theia collided with Earth some 4.5 billion years ago and left large amounts of its iron-rich material embedded in our planet, according to a new study.
Researchers first identified the material by studying seismic waves, which travel more slowly in the denser material. The continent-sized deposits lie beneath Africa and the Pacific Ocean and are each about twice the size of the moon.
As dramatic as it may sound, our collision with a wayward, Mars-sized planet is the best-accepted theory for the origin of the moon. Energy from the impact would have melted the surface of Earth and flung material out into orbit that eventually cooled to form our satellite.
Evidence for such a cataclysmic event is not hard to find. For one, the Earth-moon system contains a surplus of angular momentum, which speaks of a forceful event in the past. And the moon contains few ...
