Because of the outstanding brightness of comet Hale–Boppreliable production rates of several moleculescould be measured over a wide range of heliocentric distances.The H2O-activity of a comet is closelyconnected with the energy balance and the composition of itssurface. It is often assumed that more volatilemolecules originate from subsurface regions. The CO observationsprovided an important data base for abetter understanding of this matter. A thermal model has beenapplied to calculate gas production rates ofHale–Bopp. The strong obliquity of the spin axis causespronounced seasonal effects and, therefore, anasymmetry of water activity with respect to perihelion. By comparingmeasured and calculated rates properties of the nucleus have been derived.
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- Crovisier, J., Leech, K., Bockelée-Morvan, D., Lellouch, E, Brooke, T. Y., M. S., Altieri, B., Keller, H. U., and Lim, T.: 1999, ‘The Spectrum of Comet Hale-Bopp as seen by ISO’, ESA SP-427 137–140.Google Scholar