PerspectivePlanetary Science

Solving the Mascon Mystery

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Science  28 Jun 2013:
Vol. 340, Issue 6140, pp. 1535-1536
DOI: 10.1126/science.1238099

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When we look at the Moon, we can see images of a man, a rabbit, and countless other analogies. These images are the figments of our imagination, inspired by the distribution of thick lava sequences, the mare basalts, that fill ancient basins that formed by large meteorite impacts early in solar system history. Still, mysteries remain hidden beneath the lunar surface. The first spacecraft in orbit around the Moon felt a stronger pull of gravity when passing over these basins, implying that a mass concentration, or “mascon,” was present there (1). Subsequent studies added to the puzzle of mascons and provided partial explanations for their formation (24). On page 1552 of this issue, 45 years after the initial discovery, Melosh et al. (5) put all the pieces together and provide the first self-consistent model for the origin of mascons.