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M. F. A'Hearn, D. D. Wellnitz, L. Woodney (UMd), P. D. Feldman, H. A. Weaver (JHU), C. Arpigny (U. Liege), R. Meier (Xerox), W. M. Jackson (UC-Davis), S. J. Kim (KyungheeU)
The interpretation of the S2 that was discovered in comet IRAS-Araki-Alcock was clouded by the inability to find it in the extant spectra of any other comets. The close approach of comet Hyakutake in 1996 enabled us to again detect S2 in a comet, this time including both ground-based and Earth-orbital observations spread over several weeks. The lack of any correlation between the S2 in comet Hyakutake with either outbursts of the comet or anomalies in the interplanetary magnetic field argues against some of the scenarios invoked in the case of IRAS-Araki-Alcock. Furthermore, the discovery of SO and SO2 in Hale-Bopp removes the most obvious obstacle to the scenario in which the S2 was produced by primordial irradiation of icy grains. We are left, therefore, with either fast chemical reactions in the innermost coma (within tens of km of the nucleus) or a direct source in the nucleus, which in turn would imply that the material had been preserved in a very cold state. We will present both the ground-based and the Earth-orbital data on S2 and we will discuss the abundance and the source of S2.
This work was supported by NASA.