An improved shadow measurement technique for constraining the morphometry of simple impact craters

Abstract

The lengths of the shadows cast within simple, bowl-shaped impact craters have been used to constrain their depths on a variety of planetary bodies. This technique, however, only yields the "true" crater depth if the shadow transects the crater center where the floor is deepest. In the past, attempts have been made to circumvent this limitation by choosing only craters where the shadow tip lies very near the crater center; but this approach may introduce serious artifacts that adversely affect the slope of the regressed depth vs. diameter data and its variance. Here we introduce an improved method for deriving depth information from shadow measurements that considers three basic shape variations of simple craters: paraboloidal, conical, and flat-floored. We show that the shape of the cast shadow can be used to constrain crater shape and we derive improved equations for finding the depths of these simple craters.