Spacecraft imaging data allow an accounting of the occurrence and character
istics of the largest craters on small asteroids and satellites. Data cover
ing Phobos, Deimos, Gaspra, Ida, Mathilde, Vesta, Amalthea, Thebe, Janus, E
pimetheus, Hyperion, and Proteus show that similar to 50% of rocky objects
support craters with diameters of 1 object mean radius (R-m), and the great
majority have more than two craters with D > 0.5R(m). The morphology of th
ese craters is consistent with gravity (g(-1)) scaling from craters on larg
er objects, The amounts of visible peripheral damage, such as fracturing ca
used by these relatively large impacts, are usually small; the best possibl
e example (Phobos) may have been assisted by tidal forces. The occurrence a
nd characteristics of these craters supports modeling results that predict
formation in gravity-controlled regimes with very large relative-sized crat
ers formed before global fragmentation occurs. (C) 1999 Academic Press.