THE FORMATION OF CRATERS BY HIGH‐SPEED PARTICLES*

Abstract

ABSTRACT Some investigators have discussed the formation of craters by high‐speed particles on the basis of experimental data taken over a limited velocity spectrum for the incident particle. Their interpretation of the data has been that the crater volume is proportional to the kinetic energy of the incident particle. In this paper, we discuss an approach to this problem that was originated by Öpik for the formation of meteorite craters. Öpik's theory is based on a hydrodynamic approximation similar to the approximation that has been successfully employed by Pugh in explaining the penetration produced by shaped‐charge jets. The estimates of the mass of a meteorite based on Öpik's theory differ radically from the estimates made by Rinehart that are based on the assumption that crater volume is proportional to the kinetic energy of the incident particle up to meteoritic velocities. The essential purpose of this paper is to reëxamine both points of view in order to illuminate the details of their differences. Experimental evidence is presented from the study of shaped‐charge jets that indicates that Rinehart's extrapolation is incorrect. The data from shaped‐charge experiments are in rough agreement with Öpik's theory.