Impact-induced mass flow effects on lunar shape and the elevation dependence of nearside maria with longitude

Lunar mass flow patterns due to bolide impacts were inferred from a spectral correlation analysis of the LP75G gravity and GLTM-2 topographic models for insight on the development of the Moon's shape and elevation dependence of nearside circular maria with longitude. The results suggest that in compensating for massive crustal unloading by bolide impacts, subsurface mass flows were constrained by the dichotomized thickness and mechanical attributes of the lunar near and far sides. On the nearside, a regionally positive selenoid reflects positive mass anomalies at the Moho, as well as the lithosphere-asthenosphere and core-mantle boundaries beneath the giant ancient pre-Nectarian Procellarum basin and the superposed Imbrium basin. The elevations of nearside circular maria for the lunar multi-ring basins exhibit a first order decrease of roughly 2 km from 270° E to 90° E and a possible second order effect that is highly correlated with the lunar selenoid. The linear trend in the surface elevations of the maria reflects the greater excavation depths of the younger basins, while the second order effect suggests that the selenoid may have constrained the mare flooding of the multi-ring basins.