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M. Küppers (Universität Bern, Switzerland)
We have developed a Monte-Carlo model of the evolution of planetary and asteroidal regolith. It calculates properties like regolith layer thickness, vertical and horizontal transport, and particle size distributions. Impactors of sizes from less than a \mum up to the largest projectiles hitting the target body are considered, allowing to investigate regolith properties on both macroscopic and microscopic scales. New theoretical and experimental results about impact consequences are incorporated. In case of variable surface gravity the trajectories of crater ejecta are calculated numerically.
We will present model results for Asteroid 433 Eros. Many observations of the regolith of Eros performed by the NEAR spacecraft can be explained with impact cratering as the only process which shapes the asteroidal surface. For example, the shallow crater size distribution on Eros (Veverka et al., Science 292, 484) is a consequence of the shallower distribution of projectile sizes in the asteroid belt compared to the Earth' moon in combination with the shorter life time of small craters against infilling by regolith from subsequent impacts. The large number of boulders on the the surface of Eros can also be partly explained by the impactor size distribution. There are relatively few small, ``boulder destroying" impacts for each large impact which creates new boulders from the bedrock on Eros.
The regolith distribution on Eros is highly inhomogenous. The accumulated regolith layer thickness in the model varies between several tens of meters and less than a meter. It is not clear from the model if surface exposures of bedrock are expected.
The author(s) of this abstract have provided an email address for comments about the abstract: kueppers@phim.unibe.ch