Apollo 11: Implications for the early history of the solar system


  • John A. O'Keefe


In this paper, I shall attempt to show that the Apollo 11 data support the idea that the moon was formed by the breakup of the earth, and that they suggest that after the breakup, the moon went through a heating episode that boiled away most of its mass. I will go on to discuss the possibility that the planets of the solar system might have been formed in a similar way, that is by breakdown of Jupiter-sized objects rather than by buildup from smaller ones.

From the cosmological standpoint, the most interesting results from the Apollo 11 samples were the chemical measurements. To appreciate these, it is necessary to have some idea as to what the chemical measurements should have shown. In other words, if the moon had formed from the primeval materials of the system, what would a chemical analysis have been like? The answer to this question is called the cosmic abundance scheme. In this scheme, hydrogen forms 90% of the material, helium 10%, and the other elements, including the nonvolatile elements, constitute less than 1%. The element abundances have a fixed ratio to one another; that is, there is a definite answer to the question: What was the initial ratio of silicon to iron? A systematic listing of these ratios was first done by Henry Norris Russell in the 1930's. The most recent and useful table is by Cameron [1968].