Physical Processes on Interplanetary Dust

Abstract

This chapter discusses physical processes affecting interplanetary dust grains, including processes determining dust formation, growth, disruption, and alteration. Computer simulations and laboratory studies of coagulation and aggregation show that mutual collisions between solid grains determine the growth of solid aggregates in the early solar system when the impact energies are too low to destroy the colliding grains. On the other hand, fragmentation occurs at the high impact energies that currently prevail, generating dust from meteoroids, asteroid, and satellite surfaces as well as from sublimating comets. Such impact processes are discussed based on a compilation of laboratory measurements (e.g., size, shape, velocity and spin distributions of fragments). Gradual alteration of the dust grains occurs in the present solar system due to solar radiation and energetic particle impact. Sublimation, sputtering and charging can alter the nature of interplanetary dust grains. Dust grain temperatures, erosion rates due to solar-wind-induced sputtering, and surface charges are studied. The evidence for alteration of physical/chemical/mineralogical properties of interplanetary dust grains is still rather poor. Therefore, we discuss the expected changes, referring to those physical processes that can be simulated in laboratory experiments, and to their analogues obtained through theoretical modeling.