THE LUNAR CRUST - GLOBAL STRUCTURE AND SIGNATURE OF MAJOR BASINS

New lunar gravity and topography data from the Clementine Mission prov ide a global Bouguer anomaly map corrected for the gravitational attra ction of mare fill in mascon basins. Most of the gravity signal remain ing after corrections for the attraction of topography and mare fill c an be attributed to variations in depth to the lunar Moho and therefor e crustal thickness. The large range of global crustal thickness (simi lar to 20-120 km) is indicative of major spatial variations in melting of the lunar exterior and/or significant impact-related redistributio n. The 61-km average crustal thickness, constrained by a depth-to-Moho measured during the Apollo 12 and 14 missions, is preferentially dist ributed toward the farside, accounting for much of the offset in cente r-of-figure from the center-of-mass. While the average farside thickne ss is 12 km greater than the nearside, the distribution is nonuniform, with dramatic thinning beneath the farside, South Pole-Aitken basin. With the global crustal thickness map as a constraint, regional invers ions of gravity and topography resolve the crustal structure of major mascon basins to half wavelengths of 150 km, In order to yield crustal thickness maps with the maximum horizontal resolution permitted by th e data, the downward continuation of the Bouguer gravity is stabilized by a three-dimensional, minimum-slope and curvature algorithm. Both m are and non-mare basins are characterized by a central upwarped moho t hat is surrounded by rings of thickened crust lying mainly within the basin rims. The inferred relief at this density interface suggests a d eep structural component to the surficial features of multiring lunar impact basins. For large (>300 km diameter) basins, moho relief appear s uncorrelated with diameter, but is negatively correlated with basin age. In several cases, it appears that the multiring structures were o ut of isostatic equilibrium prior to mare emplacement, suggesting that the lithosphere was strong enough to maintain their state of stress t o the present.