Impacts on asteroids: Fragmentation, regolith transport, and disruption
Icarus, 153 (1):
1--15 (2001)Abstract
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. (C) 2001 Academic Press.