A New View Of The Moon In Light Of Data From Clementine And Prospector Missions

Results from the 1994 Clementine and 1998-1999 Lunar Prospector orbital missions are forcing a reevaluation of existing models of the origin and evolution of the moon. Data on global topography and gravity from Clementine gravity and LIDAR experiments indicate a 16 km elevation range on the farside of the moon and a wide range in computed crustal thickness. The data confirm the presence of mascons under mare-filled basins and validate earlier models of lunar hemispherical asymmetry. High resolution global maps of FeO and TiO2 derived from the Clementine UV-VIS data and Th maps from the Prospector gamma-ray data indicate that the lunar crust and the uppermost lunar mantle are laterally and vertically inhomogeneous on a global scale. An area of enhanced Th (and other incompatible element) abundances, known as the Procellarum KREEP Terrane (PKT), makes up approximately 16 percent of the nearside lunar surface. Although the highest Th abundances appear to be in upper crustal impact deposits, the close association of mare basalts with the PKT indicates that anomalously high Th, U, and K concentrations extend to mantle depths. Anorthosites are very rare within the PKT and the pre-mare crust in this region is composed of breccias and pristine rocks of the magnesian-suite and alkali-suite. (Author)