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Evidence for methane and ammonia in the coma of comet P/Halley

Allen, M. and Delitsky, M. and Huntress, W. and Yung, Y. and Ip, W.-H. and Schwenn, R. and Rosenbauer, H. and Shelley, E. and Balsiger, H. and Geiss, J. (1987) Evidence for methane and ammonia in the coma of comet P/Halley. Astronomy and Astrophysics, 187 (1-2). pp. 502-512. ISSN 0004-6361.

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Methane and ammonia abundances in the coma of Halley are derived from Giotto IMS data using an Eulerian model of chemical and physical processes inside the contact surface to simulate Giotto HIS ion mass spectral data for mass-to-charge ratios (m/q) from 15 to 19. The ratio m/q = 19/18 as a function of distance from the nucleus is not reproduced by a model for a pure water coma. It is necessary to include the presence of NH_3 , and uniquely NH_3 , in coma gases in order to explain the data. A ratio of production rates Q(NH_3)/Q(H20) = 0.01-Q.02 results in model values approximating the Giotto data. Methane is identified as the most probable source of the distinct peak at m/q = 15. The observations are fit best with Q(CH_4)/Q(H_20) = 0.02. The chemical composition of the comet nucleus implied by these production rate ratios is unlike that of the outer planets. On the other hand, there are also significant differences from observations of gas phase interstellar material.

Item Type:Article
Related URLs:
URLURL TypeDescription
Yung, Y.0000-0002-4263-2562
Ip, W.-H.0000-0002-3140-5014
Additional Information:© 1987 European Southern Observatory. Received February 10; accepted April 30, 1987. This work represents one phase of research carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract to the National Aeronautics and Space Administration. Partial support also was received from NASA grant NSG-7376 to the California Institute of Technology. The Giotto IMS experiment was supported by the National Aeronautics and Space Administration, the German Bundesministerium für Forschung und Technologie, and the Swiss National Science Foundation.
Funding AgencyGrant Number
Bundesministerium für Forschung und Technologie (BMFT)UNSPECIFIED
Swiss National Science Foundation (SNSF)UNSPECIFIED
Subject Keywords:atomic and molecular processes; comets
Issue or Number:1-2
Record Number:CaltechAUTHORS:20140909-090832242
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49482
Deposited On:10 Sep 2014 18:37
Last Modified:19 Nov 2019 00:54

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