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O. Mousis, D. Gautier (DESPA, URA 264, Obs. de Meudon, France), F. Robert (Lab. de Mineralogie, CNRS-ESA 7058, Museum d'Histoire Naturelle, France), B. Dubrulle (CNRS, UPR 182, Service d'Astrophysique, CEA/Saclay, L'Orme des Merisiers, France)
The analytical model developed in Drouart et al., (1999) for the solar nebula is used to interpret, through the integration of the equation of diffusion, the HCN D/H ratio observed in Hale-Bopp comet. By comparing with the D/H ratios measured in water in Halley, Hyakutake and Hale-Bopp comets, we constrain the heliocentric distance range and the time interval in which the comets of the Oort cloud were formed in the nebula. As previously shown for water (drouart et al., 1999), icy HCN grains originating from the presolar cloud and strongly enriched in deuterium with respect to the protosolar value, have been reprocessed in the nebula prior to the formation of comets. Isotopic exchange with molecular hydrogen and mixing in the turbulent nebula govern this isotopic reset. Accordingly, the presolar D/H ratio in HCN is estimated to lie between 4 and 8.10-3.
Drouart et al., Icarus, 1999 (in press)
The author(s) of this abstract have provided an email address for comments about the abstract: mousis@chimie.univ-nantes.fr