Sources of Interplanetary Dust

Abstract

Asteroids, comets and interstellar dust are possible sources of the particles that constitute the dust in the inner solar system. Each of these components gives rise to particular, characteristic features, the amplitudes of which can be used to estimate the size of the associated source. The asteroidal component feeds the dust bands and the Earth's resonant ring, while the cometary component may account for the large scale height of the zodiacal cloud observed at 1 AU Previous discussions of the observed strengths of these various features indicated that the source of about one third of the thermal flux observed, for example, in the IRAS 25μm waveband is asteroidal, while two thirds is cometary. However, a variety of assumptions go into this calculation (the size-frequency distribution of the particles is particularly significant) and we now know that the result is highly dependent on these assumptions. The zodiacal cloud is also the source of the IDPs collected on Earth. Because of strong gravitational focusing by the Earth of particles in low e and I orbits, it is probable that the majority of IDPs originate from asteroids, particularly those asteroids in the Themis and Koronis families.