On estimation of mass ablation of meteorites based on studies of cosmic-ray tracks

Observations of cosmic-ray tracks in silicate grains in chondrites and in stony-iron meteorites have long been recognized to be useful for the study of effective shielding depths in a preatmospheric body. In this paper we discuss ways of estimating the preatmospheric radius or mass of the original body from such observations. We consider various cases of ablation and methods to determine the magnitude of ablation in each case. In cases where a single stone survives, a determination of shielding depths in several representative samples from the surface of the stone allows a fairly accurate reconstruction of the preatmospheric shape, provided ablation is not too asymmetric. In the case of asymmetric ablation the preatmospheric radius and the magnitude of ablation can be determined from the frequency distribution of shielding depths of samples from the surface and/or from a study of shielding depths along a slice cut from the recovered stone. If, instead, the ablationary processes lead to production of a large number of stones, an estimation of the lowest track density should in most cases allow a fairly precise value of the preatmospheric radius. We also discuss a method for the estimation of mass wastage from concentric shells in the preatmospheric body based on a representative study of the distribution of surviving mass in suitably chosen track-density intervals.