Density structures beneath the lunar mascon basins from constrained inversion of gravity anomalies

The lunar mascon basins formed resulting from the impact excavation and collapse followed by isostatic adjustment and cooling and contraction of a voluminous melt pool according to the recent study. We are now interesting in the present density structures beneath the basins in order to reveal the heterogeneities. A 3-D inversion method of gravity data formulated with specially designed model objective function and radial weighting function in the spherical coordinates has been developed. We further introduce the constraints in the inverse method such as the prior parameters of density, the crustal thickness, seismic wave velocities and mineral information. The gravity anomalies of major mascon basins were calculated from the newly gravity field model, GL0660B, and the topography model, LRO_LTM02, and the gravity effects of lava fills. Constrained inversions of gravity anomalies were then performed for several basins. We show that the density structures of mascon basins are lateral heterogeneities and different from each other although the dense materials of mantle concentrates at depth of 10-50 km. These heterogeneities are suggested resulting from the impactors and the lunar thermal stage at times. This research is supported by the Special Fund for Basic Scientific Research of Central Colleges, China University of Geosciences (Wuhan) (Grant No. CUG100701 and No. CUG130106) and the National Natural Science Foundation of China (Grant No. 41104048).