The comet nucleus: ice and dust morphological balances in a production surface of comet P/Halley.

Abstract

Dust-to-gas mass ratios are presented based on in situ measurements of the coma dust and gas distributions of comet P/Halley by the DIDSY, PIA, and NMS experiments aboard the Giotto spacecraft. A relative excess, compared with preflight expectations, of particulates with masses >10^-9kg is observed; if this is representative of the coma as a whole, the dust-to-gas ratio, μ, within the nucleus must be about 2. This compares with a value of μ ≡ 0.2 for a model distribution without a large particle excess. The implied mass and area distributions of particulates in the parent nucleus material is presented for observed and modeled coma distributions. Some basic properties expected of the surface material are identified that are relevant to nucleus modeling and to the remote sensing of nucleus material during cometary rendezvous.