Cratering on Mathilde

Abstract

Crater populations on Mathilde are assessed from NEAR flyby images. Small to intermediate-sized craters (1/2 to 5 km diameter) approach saturation equilibrium spatial densities and exhibit a range of degradation states similar to the crater populations on Ida. They probably represent a population in quasi-equilibrium between the creation and the destruction of craters caused by saturated impacts on Mathilde. Very large craters, with diameters approaching or exceeding the average radius of Mathilde itself, dominate the shape of Mathilde and represent a uniquely high spatial density of craters on a planetary surface. Formation of these large craters were remarkably ineffective in modifying, let alone destroying, preexisting topography. We speculate that Mathilde's retention of so many large, relatively well-preserved craters may be due to its bulk material properties and/or rubble-pile internal structure. The overall crater populations on Mathilde are consistent with (although do not uniquely require) the same production function (i.e., same projectile power-law size distribution) observed in the cratering records of the Moon, Gaspra, and (apparently) Ida.