Abundances in Comet Halley at the time of the spacecraft encounters

Wyckoff, Susan and Tegler, Stephen and Wehinger, Peter A. and Spinrad, Hyron and Belton, Michael J. S. (1988) Abundances in Comet Halley at the time of the spacecraft encounters. The Astrophysical Journal, 325. pp. 927-938. ISSN 1538-4357

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Abstract

Spectrophotometric observations of Comet Halley obtained in March 1986 at the time of the spacecraft encounters with the comet are described, and the column densities derived from the integrated emission band fluxes are presented. The scale lengths are determined from the spatial profiles of the observed species. Production rates are derived and the parent identities and abundance ratios of the studied species are discussed. The data indicate that the abundance of the primordial condensate NH3 comprises about 0.2 percent of the total volatile fraction of the comet nucleus. The ratio of production rates Q(NH2)/Q(H2O) = 0.003 indicates that Q(NH3)/Q(H2O) is roughly 0.3 percent, which is nearly 10 times lower than the value determined from Giotto ion mass spectrometer data. The production rate Q(CH)/Q(H2O) of 0.007 and the CH spatial profile indicate that CH cannot derive entirely from direct photodissociation of CH4.

Item Type:	Article
Publisher’s Statement:	© The American Astronomical Society. Published in Astrophysical Journal, Part 1.
ID number or DOI:	10.1086/166064
Keywords:	abundance; accretion disks; brightness; Brightness Distribution; C2 Radical; Calculations; chemical composition; CH Radical; Cometary Atmospheres; Comet Nuclei; Comets; Comet Tails; comparisons; decay; Distribution; Earth-based Observations; flux; Flyby Missions; Formation; Halley; Halley'S Comet; models; Neutral Particles; NH2 Radical; origin; Parent Molecules; Photodissociation; Production Rates; Source; spatial distribution; spectra; Spectrophotometry; sublimation; Surface
Subjects:	Q Science > QB Astronomy
NAU Depositing Author Academic Status:	Faculty/Staff
Department/Unit:	College of Engineering, Forestry, and Natural Science > Physics and Astronomy
Date Deposited:	19 Nov 2015 00:41
URI:	http://openknowledge.nau.edu/id/eprint/1846

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