Alastair G. W. Cameron employer University of Arizona
Formation of the Moon
Samples brought back from the Apollo program showed that the Moon was composed of the same material as the mantle of the Earth. This surprising result was still unexplained in the early 1970s, when Cameron began work on an explanation of the Moon's origins. He theorized that the formation of the Moon was the result of a tangential impact of an object at least the size of Mars on the early Earth. In this model, the outer silicates of the body hitting the Earth would be vaporized, whereas a metallic core would not. The more volatile materials that were emitted during the collision would escape the Solar System, whereas silicates would tend to coalesce. Hence, most of the collisional material sent into orbit would consist of silicates, leaving the coalescing Moon deficient in iron and volatile materials, such as water.
After seeing William Hartmann present a similar, independent model at a conference in 1974, Cameron began a several decade-long collaboration with Hartmann to develop the giant-impact hypothesis. Cameron was able to use increasingly sophisticated computer models to show that such a collision could produce an Earth-Moon system with the correct mass, spin, and orbital momentum. The giant-impact theory gained mainstream acceptance as the scientific explanation for the origin of the Moon beginning in the 1980s.After his retirement from Harvard in 1999, Cameron held a position at the Lunar and Planetary Laboratory of the University of Arizona.
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