The Origin of Lunar Mascon Basins

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Science  30 May 2013:
DOI: 10.1126/science.1235768

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High-resolution gravity data from the GRAIL spacecraft have clarified the origin of lunar mascons. Free-air gravity anomalies over lunar impact basins display bulls-eye patterns consisting of a central positive (mascon) anomaly, a surrounding negative collar, and a positive outer annulus. We show that this pattern results from impact basin excavation and collapse followed by isostatic adjustment and cooling and contraction of a voluminous melt pool. We employed a hydrocode to simulate the impact and a self-consistent finite-element model to simulate the subsequent viscoelastic relaxation and cooling. The primary parameters controlling the modeled gravity signatures of mascon basins are the impactor energy, the lunar thermal gradient at the time of impact, the crustal thickness, and the extent of volcanic fill.

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