Dust in comet P/Halley from Vega observations

Abstract

Direct measurements of the dust particle spatial and mass distributions in comet Halley have been carried out on Vega spacecraft over the mass range ˜10-16 - 10-6g with the SP-2 dust particle detector consisting of a set of acoustic and impact plasma sensors. These measurements have revealed a large-scale, time-variable structure of the dust coma, the position and characteristics of its boundaries, and a strongly pronounced angular directivity of dust emission from the cometary nucleus. An unexpectedly high concentration of tiny dust particles with masses below 10-14g and strong systematic variations of the shape of the particle mass distribution as a function of distance to the cometary nucleus have been observed. The mean dust production rate by the nucleus has been estimated at (10 - 13)×106g s-1 (Vega 1) and (5 - 7)×106g s-1 (Vega 2).