Systematics of the CHON and Other Light Element Particle Populations in Comet p/ Halley

Abstract

Based on chemical signatures measured by the PIA experiment during the Giotto flyby of comet P/Halley, a number of particle classifications have been designated. In addition to silicate-like grains and particles of mixed (cosmic) composition, there appear to be several light-element rich populations including the CHON, (H,C), (H, C, O), and (H,C,N) particle types. In some cases, these compositional classes are further distinguished by differences in mass distributions, a density indicator, and variations in relative abundance within the coma. These particle populations are evidence for chemical heterogeneity in the surface of the cometary nucleus. Some particles found mainly in the inner coma may be volatile icy grains. Most of the N of the comet may be found in up to three different populations of grains; one or more of these may be responsible for the observation of cyanojets.