Variations in lunar elastic thickness from admittance spectral analysis

Abstract

We infer the elastic thickness of regions of the Moon by performing an admittance analysis on GRAIL gravity and LOLA topography data. Reliable results are generally confined to the lunar farside, away from large mare deposits. We find that elastic thickness varies between 13 km and 72 km, with a mean elastic thickness (Te) of 29 km. The highest reliable elastic thicknesses are found to the northwest of South Pole-Aitken (SPA) basin while the lowest elastic thicknesses are found in the equatorial farside and within SPA. Our findings suggest that much of the loading on the Moon must have taken place within the first 200 Myr after lunar magma ocean solidification, though some areas (Te > 40 km) may be recording events as late at 3.5 Ga. We find no correlation between elastic thickness and crater density, crustal thickness, or mean elevation in areas where reliable estimates of elastic thickness can be made, though we do note that regions with the highest crustal thickness and mean elevation are associated with lower elastic thickness values. We also demonstrate that smaller localization windows can lead to systematically lower elastic thickness estimates.