Modelling the Disruption and Reaccumulation of Miranda

V. Vanzani, F. Marzari (Univ. Padova), D. R. Davis, S. J. Weidenschilling (PSI), E. Dotto (Univ. Padova)

The heavily cratered surfaces of the largest Uranian satellites and the unusual surface geology of Miranda suggest that these bodies could have been catastrophically disrupted by collision and then reaccumulated over solar system history (Smith et al., 1986; Mckinnon et al., 1991).

Using the model described by Marzari et al. (1995, Icarus 113, 168) we have simulated the breakup of Miranda by a high velocity impact. With this model we have produced realistic initial conditions for the numerical algorithm of Spaute et al. (1992, Icarus 92, 147) which has been used to model the subsequent reaccumulation of the satellite from the ring of fragments. All the possible outcomes of two body collisions are considered in the model of Spaute et al. (1992): accretion, inelastic rebound, cratering and fragmentation.

Our numerical simulations show that the reaccumulation of Miranda occurs on a short timescale ( tex2html_wrap_inline15 years) in spite of the initial large dispersion of the ring debris and the presence of Ariel at the outer border of the ring. The reaccumulation is characterized by two stages. An initial stage during which shattering and cratering dominate and all bodies smaller than 20 km are destroyed. In the second stage the large survived fragments grow by accumulating the small comminuted fragments and finally, colliding each other, rebuild a new Miranda.