Dust jets in comet Halley observed by Giotto and from the ground

Abstract

A first map of discrete dust-emission sources on the nucleus of comet Halley was recently completed, based on a study of the morphology of 55 features (jets, spirals, envelopes and others) recognized and modelled on 34 digitally processed plates of the comet obtained during May and June of 1910. A brief progress report¹ and a preliminary version of the map² have already been published, while the detailed technical paper is in press³. In the process of fitting the dust features, an earlier determination⁴ of the nucleus spin vector in 1910—a necessary prerequisite for mapping the sources—was refined^1,3. Here we assess the relevance of our results based on the 1910 observations to the comet's current apparition, using data obtained by the Giotto spacecraft of the European Space Agency (ESA) and from ground-based observations. The problems involved are possible variations in the spin vector over the 76-yr period, survival of the dust sources, and the positions of the prime meridian at the two returns to the Sun. Evidence from ground-based and spacecraft imaging of dust jets is compared and the distribution of discrete dust sources on the nucleus surface studied.