Perspectives on Interstellar Dust Inside and Outside of the Heliosphere

Measurements by dust detectors on interplanetary spacecraft appear to indicate a substantial flux of interstellar particles with masses > 10−12 g. The reported abundance of these massive grains cannot be typical of interstellar gas: it is incompatible with both interstellar elemental abundances and the observed extinction properties of the interstellar dust population. We discuss the likelihood that the Solar System is by chance located near an unusual concentration of massive grains and conclude that this is unlikely, unless dynamical processes in the ISM are responsible for such concentrations. Radiation pressure might conceivably drive large grains into “magnetic valleys”. If the influx direction of interstellar gas and dust is varying on a ∼ 10 yr timescale, as suggested by some observations, this would have dramatic implications for the small-scale structure of the interstellar medium.