Gravity anomalies and crustal structure of the Lunar far side highlands

Abstract

The far side of the lunar hemisphere is dominated by a large number of impact craters having a smaller diameter and few Mare basins compared to the near side of the Moon. This study presents a detailed analyses of gravity anomalies derived from Gravity Recovery and Interior Laboratory (GRAIL) mission and topography over the central equatorial region of Lunar far side covering the major impact basins such as Dirichlet-Jackson, Korolev, Hertzsprung and adjoining regions of the highlands, to understand sub-surface structure. Bouguer gravity anomaly map of the region is prepared using the density of 2.7 g/cc, which is estimated using fractals based approach. The spectral analyses using Maximum Entropy Method of calculated Bouguer anomaly and topography provided an estimated of Effective Elastic Thickness (Te) as 19 km and also a cut-off wavelength of 270 km for separating Regional and residual Bouguer gravity anomalies. Further a crustal thickness of this region of Moon is estimated by inversion of regional Bouguer gravity anomalies, which varies from 20 to 71 km.An estimated crustal thickness of Dirichlet Jackson and Hertzpsrung, Korolev basins varies between 39 and 65 km, 20–65 km and 39–64 km, respectively. The residual gravity anomaly map shows symmetric gravity highs and lows in Dirichlet-Jackson, Hertzsprung and Korolev basins. These gravity highs can be attributed to high-density mare basalts within inner rims of these basins. The observed nature of gravity anomalies and crustal thickness map can be attributed to the buried impact crater under this region.