Large Craters on Small Objects: Occurrence, Morphology, and Effects

Abstract

Spacecraft imaging data allow an accounting of the occurrence and characteristics of the largest craters on small asteroids and satellites. Data covering Phobos, Deimos, Gaspra, Ida, Mathilde, Vesta, Amalthea, Thebe, Janus, Epimetheus, Hyperion, and Proteus show that ~50% of rocky objects support craters with diameters of 1 object mean radius (Rm), and the great majority have more than two craters with D>0.5 Rm. The morphology of these craters is consistent with gravity (g-1) scaling from craters on larger objects. The amounts of visible peripheral damage, such as fracturing caused by these relatively large impacts, are usually small; the best possible example (Phobos) may have been assisted by tidal forces. The occurrence and characteristics of these craters supports modeling results that predict formation in gravity-controlled regimes with very large relative-sized craters formed before global fragmentation occurs. © 1999 Academic Press.