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Limit on the CH4/CO ratio in Comet Levy (1990c) and comparisons with other cometsNear-infrared observations of comet Levy (1900c) were made on UT 4.3 and 5.3 Sep. 1990 from the United Kingdom Infrared Telescope on Mauna Kea. A scanning Fabry-Perot interferometer in combination with a cooled grating spectrometer was used to make a sensitive search for fluorescent emission from the v zub 3 band of CH4 near lambda approx. 3.3 microns. If CH4 is a parent molecule released directly from the nucleus, then the 3 sigma limit on its abundance is CH4/H2O approx. less than 0.0031, assuming that the kinetic temperature of the inner coma is approx. 50 K and that the CH4 spin species are equilibrated at a temperature approx. greater than 50 K. Since International Ultraviolet Explorer (IUE) observations of CO in Levy indicate that CO/H2O approx. 0.04 (Feldman et al.), researchers find that CH4/CO approx. less than 0.1. Infrared spectroscopic searches for CH4 in Comet Halley also yielded no positive detections; the more sensitive upper limit from the latter observations is CH4/H2O approx. less than 0.002. Since CO/H2O approx. 0.05 in Halley (not including the extended source of CO), the upper limits on the CH4/CO ratios are almost identical for comets Levy and Halley. A marginal infrared detection of the CH4 v sub 3 band in comet Wilson yielded CH4/H2O approx. 0.01 to 0.05 (Larson et al.), but there was no positive detection of CO. If the identification of the feature in the infrared spectrum of comet Wilson is correct, then that would indicate a very high CH4/CO ratio in this comet.
Document ID
19910016699
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Weaver, Harold A. (Space Telescope Science Inst. Baltimore, MD., United States)
Chin, G. (NASA Goddard Space Flight Center Greenbelt, MD., United States)
Brooke, T. Y. (NASA Goddard Space Flight Center Greenbelt, MD., United States)
Tokunaga, A. T. (NASA Goddard Space Flight Center Greenbelt, MD., United States)
Geballe, T. R. (Joint Astronomy Centre Hilo, HI., United States)
Date Acquired
September 6, 2013
Publication Date
January 1, 1991
Publication Information
Publication: Lunar and Planetary Inst., Abstracts for the International Conference on Asteroids, Comets, Meteors 1991
Subject Category
Astrophysics
Accession Number
91N26013
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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