Hypervelocity experiments of impact cratering and catastrophic disruption of targets representative of minor bodies of the Solar System

Impact processes influence the surface evolution of the solid bodies in the Solar System, as asteroids or comets. The better understanding of these phenomena can improve the interpretation of remote sensing data from forthcoming missions. In order to complement and to extend the available data on hypervelocity impacts on porous targets to ranges of velocity and physical conditions not yet explored, we focused our work on catastrophic fragmentation and cratering processes onto porous targets by means of high velocity impact experiments using a two-stage light-gas gun located at the impact facility of CISAS "G. Colombo" of the University of Padova. Tests have been performed on targets of different materials, e.g. glass ceramic foam, natural pumices, water ice, and different porosity (with density in the range from 0.35 to 1.07 g/cm(3) and porosity from 2% up to 65%). Results have been analysed and compared to published data. In particular, cratering morphology is studied as function of projectile velocity and density and then it is compared to empirical trend reported in Kadono [Kadono, T. Hypervelocity impact into low density material and cometary outburst. Planet. Space Sci., 47, 305-318 1999.] with good agreement. Our tests results revealed that porosity seems to induce a rapid attenuation of the shock affecting energy propagation inside the target; craters generated by hypervelocity impacts on porous targets are smaller and much deeper than those of non porous targets. Fragments distribution resulting from disruption tests is analysed and the largest fragment mass has been studied as function of the collisional specific energy; results is compared to those of paper by Ryan et al. [Ryan, EN., Davis, DR., Giblin, I. A laboratory impact study of simulated edgeworth-Kuiper belt objects. Icarus 142, 56-62, 1999.]. Furthermore, numerical simulations have been performed by using Smooth Particle Hydrodynamics (SPH) and Lagrangian grid technique in order to test some available numerical models for a forthcoming more accurate numerical analysis that will be validated with the comparison with experimental results. (C) 2007 COSPAR. Published by Elsevier Ltd. All rights reserved.