The global effects of impact-induced seismic activity on fractured asteroid surface morphology

Impact-induced seismic vibrations have long been Suspected of being in important surface modification process oil small satellites and asteroids. In this Study, we use a series of linked seismic and geomorphic models to investigate the process in detail. We begin by developing a basic theory for the propagation of seismic energy in it highly fractured asteroid, and we use this theory to model the global vibrations experienced oil the surface of all asteroid following ail impact. These synthetic seismograms are then applied to a model of regolith resting on a slope, and the resulting downslope motion is computed for it full range of impactor sizes. Next, this computed downslope regolith flow is used in a morphological model of impact crater degradation and erasure, showing low topographic erosion accumulates as a function of time and the number of impacts. Finally, these results are applied in it stochastic cratering model for the surface of ail Eros-like body (same volume and Surface area as the asteroid), with craters formed by impacts and then erased by the effects of superposing craters, ejecta coverage, and seismic shakedown. This simulation shows good agreement with the observed 433 Eros cratering record at a Main Belt exposure age of 400 +/- 200 Myr, including the observed paucity of small craters. The lowered equilibrium numbers (loss rate = production rate) for craters less than similar to 100 m in diameter is a direct result of seismic erasure, which requires less than it meter of mobilized regolith to reproduce the NEAR observations. This study also points to an upper limit on asteroid size for experiencing global, surface-modifying, seismic effects from individual impacts of about 70-100 km (depending upon asteroid seismic properties). Larger asteroids will experience only localized (regional) seismic effects from individual impacts. (c) 2005 Elsevier Inc. All rights reserved.