Impact cratering in viscous targets - Laboratory experimentsTo determine the effects of target yield strength and viscosity on the formation and morphology of Martian multilobed, slosh and rampart-type impact craters, 75 experiments in which target properties and impact energies were varied were carried out for high-speed motion picture observation in keeping with the following sequence: (1) projectile initial impact; (2) crater excavation and rise of ejecta plume; (3) formation of a transient central mound which generates a surge of material upon collapse that can partly override the plume deposit; and (4) oscillation of the central mound with progressively smaller surges of material leaving the crater. A dimensional analysis of the experimental results indicates that the dimensions of the central mound are proportional to (1) the energy of the impacting projectile and (2) to the inverse of both the yield strength and viscosity of the target material, and it is determined that extrapolation of these results to large Martian craters requires an effective surface layer viscosity of less than 10 to the 10th poise. These results may also be applicable to impacts on outer planet satellites composed of ice-silicate mixtures.
Document ID
19820038840
Acquisition Source
Legacy CDMS
Document Type
Conference Proceedings
Authors
Greeley, R. (NASA Ames Research Center Space Sciences Div., Moffett Field, CA; Arizona State University, Tempe, AZ, United States)
Fink, J. (NASA Ames Research Center Moffett Field, CA, United States)
Snyder, D. B. (Arizona State University Tempe, AZ, United States)
Gault, D. E. (Murphys Center for Planetology Murphys, CA, United States)
Guest, J. E. (London, University Observatory, Mill Hill, Middx., United Kingdom)
Schultz, P. H. (Lunar and Planetary Institute Houston, TX, United States)