IMPROVEMENTS TO THE EPSILON-ALPHA POROSITY MODEL FOR IMPACT SIMULATIONS.

G. S. Collins 1 , H. J. Melosh 2 , C. R. Wilson 3 and K. Wunnemann 3 , 1 Impacts and Astromaterials Research Centre, Dept. Earth Science and Engineering, Imperial College London, London SW7 2AZ, UK (g.collins@imperial.ac.uk), 2 Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette, USA, 3 Museum fur Naturkunde, Leibniz-Institute at the Humboldt University, D-10099 Berlin, Germany.