Identification and Quantification of Water in Comet C/1996 B2 (Hyakutake) and Comet C/1995 01 (Hale-Bopp) Using Infrared Hot-Band Fluorescence

N. Dello Russo, M. J. Mumma, M. A. DiSanti (NASA-GSFC), K. Magee-Sauer, D. Greenspan (Rowan College), R. Novak (Iona College), T. Rettig (Notre Dame University)

Water is the dominant volatile constituent in comets, and the species to which other molecular production rates are compared. Ground-based detection of cometary water is normally impossible because of severe extinction by terrestrial water. We developed a method for detecting water in comets by hot-band fluorescence in the infrared which we have demonstrated for three vibrational bands. Using this approach, a production rate, rotational temperature and ortho/para ratio was determined for water in Comet C/1996 B2 from late March to early April, 1996. Observations from January to May, 1997 on Comet C/1995 01 have provided a rotational temperature and ortho/para ratio for water as well as the production rate as a function of heliocentric distance. These observations were made using the CSHELL cryogenic grating spectrometer at the NASA Infrared Telescope Facility on Mauna Kea.