title: The origin of lunar mascon basins.
abstract: High-resolution gravity data from the Gravity Recovery and Interior Laboratory spacecraft have clarified the origin of lunar mass concentrations (mascons). Free-air gravity anomalies over lunar impact basins display bull's-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 used 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.
authors.affiliation: Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN 47907, USA. jmelosh@purdue.edu
authors.forename: H J
authors.initials: HJ
authors.lastname: Melosh
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Freed
authors.forename: Brandon C
authors.initials: BC
authors.lastname: Johnson
authors.forename: David M
authors.initials: DM
authors.lastname: Blair
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Andrews-Hanna
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Neumann
authors.forename: Roger J
authors.initials: RJ
authors.lastname: Phillips
authors.forename: David E
authors.initials: DE
authors.lastname: Smith
authors.forename: Sean C
authors.initials: SC
authors.lastname: Solomon
authors.forename: Mark A
authors.initials: MA
authors.lastname: Wieczorek
authors.forename: Maria T
authors.initials: MT
authors.lastname: Zuber