The topography and gravity of Mare Serenitatis: implications for subsidence of the mare surface

The long wavelength topography of Mare Serenitatis was analyzed using topographic data obtained by the Clementine laser ranging instrument (LIDAR). The topography shows that the lowest elevations in the mare surface occur near the margins of the basin. The present mare surface reflects a long period of volcanism, subsidence, and deformation. Subsidence is generally attributed to a Gaussian-shaped, superisostatic load from the mare basalts that results in flexure of the lunar lithosphere. Gravity data from Lunar Prospector suggest that the basalt sequence in the interior of Serenitatis is generally uniform in thickness and thins rapidly at the margins. This suggests that the topographic lows in the basin do not coincide with areas where the mare basalts are thick but rather occur where the basalts thin. The topographic lows also do not appear to coincide with accumulations of the youngest mare basalt units. The long wavelength topography of Mare Serenitatis may reflect subsidence influenced by pre-mare basalt basin topography and preexisting zones of lithospheric weakness.