Meteoritic Spherules in the Soil surrounding Terrestrial Impact Craters

Abstract

ANALYSES of lunar material returned by the Apollo missions¹ will raise many questions regarding the formation of splatter particles distributed about the lunar surface by meteoritic impacts, and we report here some results of our searches for and studies of microscopic (10–300 µm) meteoritic particles in the soil surrounding five terrestrial meteorite craters: Sikhote-Alin, Canyon Diablo, Odessa, Boxhole and Henbury. Our aim was to search for particles that had their origin in the cratering process and to investigate their chemical and physical properties. Because of the difficulties of identifying small particles in soil samples, we have limited our attention so far to the magnetic component. Thus our results bear only on the problem of the formation of impact particles from iron rather than from stony meteorites and that contain at least some material from the parent meteorite. We do not report here any information relevant to the problem of the nonmeteoritic impact products or those produced by impacts of chondritic meteorites. It should be noted that virtually all recognized impact craters on the Earth are produced by iron meteorites, a fact that apparently can be ascribed to the greater erosion rate for chondrites, both in interplanetary space and in the terrestrial atmosphere. The lunar surface is expected to show a greater percentage of chondritic craters than is found on Earth.