The origin of the Moon

Before the Apollo mission, a theory was constructed for the origin of the moon based on the chemical analysis of tektites as follows: The earth initially rotated in a period of about two hours. It became unstable and divided into two portions, the earth and the proto-moon, one about ten times as massive as the other. The two portions rotated in about two hours each and revolved around each other in four hours. The very large tides produced at this time heated both bodies strongly. The proto-moon in particular became gaseous. A common atmosphere was evolved which surrounded the two bodies. From it, as in the case of close double stars, a large amount of matter was lost to the system, chiefly from the proto-moon, which lost most of its mass and became the moon. Examination of the Apollo 11 samples supports these ideas. It is found that the moon is greatly depleted in the elements that went to form the earth's core, as though the moon had separated from the earth after the formation of the earth's core. It is further found that the moon has apparently passed through an episode of very severe heating, in which water, chalcophile elements, and other volatiles have been lost; and very likely large amounts of the silicates were also lost, since some refractory elements are found to be enhanced. To complete the theory, a study is made of possible mechanisms by which the earth might have been caused to rotate rapidly in the beginning. It is found very difficult to explain this spin-up unless the earth initially possessed a deep atmosphere of volatile materials somewhat like one of the major planets.