INVERSION OF CRATER MORPHOMETRIC DATA TO GAIN INSIGHT ON THE CRATERING PROCESS

In recent years, morphometric data for Venus and several outer planet satellites have been collected, so we now have observational data of c omplex craters formed in a large range of target properties. We presen t general inversion techniques that can utilize the morphometric data to quantitatively test various models of complex crater formation. The morphometric data we use in this paper are depth of a complex crater, the diameter at which the depth-diameter ratio changes, and onset dia meters for central peaks, terraces, and peak rings. We tested the role s of impactor velocities and hydrostatic pressure vs. crustal strength , and we tested the specific models of acoustic fluidization (Melosh, 1982) and nonproportional growth (Schultz, 1988). Neither the acoustic fluidization model nor the nonproportional growth in their published formulations are able to successfully reproduce the data. No dependenc e on impactor velocity is evident from our inversions. Most of the mor phometric data is consistent with a linear dependence on the ratio of crustal strength to hydrostatic pressure on a planet, or the factor c/ rho g.