Internal Constitution and Mechanisms of Asteroid Fragmentation

Abstract

It has been generally assumed in the past that the fragmentation of asteroidal bodies and the production of meteorites are solely the result of collision events. (See Dohnanyi, 1969; Hartmann and Hartmann, 1968; Wetherill, 1967.)A possible mechanism of noncollisional fragmentation will be proposed below, its proper framework of applicability will be defined, and evidence suggesting and supporting its existence will be adduced. Briefly, it is shown that the presence of even trace amounts of hydrogen in meteoritic metal phases (Edwards, 1955) may have caused the parent bodies of iron meteorites to undergo, spontaneously, delayed brittle fracture under the action of prolonged slow stresses, the imprint of which has been recorded in the phase structure of meteorites (Baldanza and Pialli, 1969). This phenomenon, termed “hydrogen embrittlement,” has been amply documented in the literature on the metallurgy of ferrous metals (Bernstein, 1970;Tetelman, 1969).