Mascons and the moon's gravity field

Abstract

The apparent surface mass M of the mascon in a lunar ringed mare is approximately proportional to the area A of the deep mare material in the basin: M∝A δ where σ lies between 0.85 and 1.20 with a most probable value of 1.02. This relationship can be interpreted in terms of thin plates of dense rock whose thickness is the same for all ringed maria. This characteristic thickness may be associated with the depth to a lunar “Moho”. For a crust-mare density contrast of 0.5 g/cm 3, the thickness of the plates would be 8.32 km. The effective diameters ( A 1 2 /π ) and the surface masses of six earthside ringed maria are listed in table 1. Effective diameters and surface masses of mascons in lunar ringed maria Mascon Mass Diameter (× 10 −6 lunar masses) (km) Serenitatis 22.44 ± 1.73 650 ± 35 Imbrium 19.40 ± 1.65 625 ± 35 Crisium 11.52 ± 1.50 450 ± 25 Nectaris 9.67 ± 1.41 420 ± 20 Fecunditatis 7.19 ± 1.41 375 ? Humorum 4.36 ± 0.87 300 ± 35 Orientale 5.25 ± 0.50 315 ± 15 Smythii 7.25 ± 0.75 370 ± 20 The mass-area relationship predicts mascons in Maria Orientale and Smythii on the west and east limbs of the Moon which are consistent with Lunar Orbiter Doppler data. These are also listed in table 1.