The origin of dust in the Solar System

Abstract

The assumption that the Zodiacal Cloud is a predominantly meteoritic rather than a meteoroidal complex is questioned. On the basis of (i) the observed exposure ages of interplanetary dust particles collected from the stratosphere, (ii) the compressive strength of the commonest fireballs, (iii) the existence of a broad ecliptic stream centred on the Taurids and (iv) the observation of substantial short-lived meteoroid swarms therein, a suitably consistent replenishment model is constructed in which the Zodiacal Cloud appears to derive from a now defunct large comet that arrived in an Earth-crossing orbit ca. 10-100 ka ago. A corollary of this model is that the latter’s remnant, a surviving large meteoroid, may be reactivated as a comet at intervals of ca. 1 ka giving rise to a variety of observable effects such as Zodiacal Cloud enhancements and rare multiple bombardments of the Earth by many bodies with masses at least 10 11 g, which typify a general process throughout Earth history responsible for climatic excursions and extinction events. It is recommended that a search be conducted for the large meteoroid or minor planet responsible for the dust now in the Solar System, to place our understanding of the latter’s evolution on a secure quantitative basis. If verified, this model would have profound implications so far as our understanding of the origin of comets is concerned because most of the cometary mass would apparently be contained in large differentiated bodies.