We use a numerical hydrocode model to examine the outcomes of various size impacts into targets the sizes of Asteroids 951 Gaspra and 243 Ida, which were imaged by the Galileo spacecraft. A shock wave fractures the asteroid in advance of crater excavation flow; thus, for impactors larger than 100 m impacting at 5.3 km s -1 , tensile strength is unimportant in these bodies, whether they are initially intact or are "rubble piles." Because of the shock-induced fracture, impact results are controlled by gravity. Therefore these asteroids are much more resistant to catastrophic disruption than predicted by previous estimates, which had assumed that strength was controlling these processes for rock targets.
The rubble and regolith produced by this fracture can be "jolted" by the impact, redistributing surface material and globally erasing craters. The crater ejecta can produce tens of meters of regolith per large event, likely consisting of 100-m-size boulders mixed with smaller particles.
The response of kilometer-size asteroids to impacts is qualitatively different from that of few-centimeter targets in terrestrial experiments, making prediction based on such experiments difficult. The compositional distribution of delivered meteorites depends on the outcomes of such asteroid impacts.