G.C. Sanzovo

Nitrogen Sulfide In Comets Hyakutake (C/1996 B2) And Hale–Bopp (C/1995 O1)

The chemistry of both nitrogen and sulfur presents interesting problems in comets. In this paper, we use a model of cometary comae with gas-phase chemical kinetics and gas dynamics to predict molecular abundances in the inner coma region for two of the brightest comets in the past 20 years, Hyakutake (C/1996 B2) and Hale-Bopp (C/1995 01). In this progress report we concentrate on the gas-phase chemistry of the nitrogen sulfide (NS) radical at a heliocentric distance of 1 AU to study the abundance of NS using a detailed photo and chemical reaction network with over 100 species and about 1000 reactions. The results are compared with recent observations of Comet Hale-Bopp and reveal that conventional gas-phase reactions schemes do not produce NS in sufficient quantities to explain the observations. We plan to continue the refinement of the model to improve agreement with observational constraints.