This is an image of the Moon showing various minerals found on the surface.
Click on image for full size
Unlike the icy moons of the outer planets, the moons of the Earth and Mars are rocky moons. We said already that the moons of Mars are probably captured asteroids. In a moment we will discuss the fact that there was still a lot of debris and small planetismals floating around at this time, crashing into the forming planets.
Currently, the theory that best explains all the evidence about the formation of the Earth's moon is that the Earth was struck by a large object, possibly as
large as Mars. This theory says that enough debris was scattered from the Earth to form the Moon. Scientists can make movies of how this crash might have worked. The movies
show that energy from such a crash produces a stream of completely vaporized
rock from the impact. It is thought that the Moon formed from this cooled material.
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