IMPROVED GRAVITY-FIELD OF THE MOON FROM LUNAR PROSPECTOR

An improved gravity model from Doppler tracking of the Lunar Prospecto r (LP) spacecraft reveals three new Large mass concentrations (mascons ) on the nearside of the moon beneath the impact basins Mare Humboltia num, Mendel-Ryberg, and Schiller-Zucchius, where the Latter basin has no visible mare fill. Although there is no direct measurement of the L unar farside gravity, LP partially resolves four mascons in the Large farside basins of Hertzsprung, Coulomb-Sarton, Freundlich-Sharonov, an d Mare Moscoviense. The center of each of these basins contains a grav ity maximum relative to the surrounding basin. The improved normalized polar moment of inertia (0.3932 +/- 0.0002) is consistent with an iro n core with a radius of 220 to 450 kilometers.