Potential anomalies on a sphere: Applications to the thickness of the lunar crust

Roger Phillips (1) , Mark Wieczorek (1)

1 WUSTL - Washington University in Saint Louis

A new technique for calculating potential anomalies on a sphere due to finite amplitude relie f has been developed. We show that by raising the topography to the nth power and expanding this field into spherical h annonics, potential anomalies due to topography on spherical density interfaces can be computed to arbitrary p recision. U sing a filter for downward continuing the Bouguer anomaly, we have computed a variety of crustal thickness maps for the Moon, assuining both a homogeneous as well as a dual-layered crust. The crustal thickness maps for the homogeneous model give plausible results, but this model is nor consistent with the seismic data, petrologi.c evidence, and geoid to topography ratios, all of which suggest some form of crustal stratification. Several dual-layered models were investigated, and it was found that only models with both upper and lower c rustal thickness variations could satisfy the gravity and topography data. These models predict that the entire upper crust has been excavat ed beneath the major nearside multiring b as itis. Additiona lly, significant amounts of lower crusta l material was excavated from these basins, especially beneath Crisium. T his m odel also predicts that mantle material should not have been excavated during the South-Pole A itken basin forming event, and that lower crus tal material should be exposed at the surface in this basin.

Domaines: Planétologie

Roger Phillips, Mark Wieczorek. Potential anomalies on a sphere: Applications to the thickness of the lunar crust. Journal of Geophysical Research. Planets, 1998, 103 (E1), pp.1715-1724. ⟨10.1029/97JE03136⟩. ⟨hal-02458509⟩