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Carbonaceous Components in the Comet Halley DustCometary grains containing large amounts of carbon and/or organic matter (CHON) were discovered by in situ measurements of comet Halley dust composition during VEGA and GIOTTO flyby missions. In this paper, we report the classification of these cometary, grains by means of cluster analysis, discuss the resulting compositional groups, and compare them with substances observed or hypothesized in meteorites, interplanetary dust particles, and the interstellar medium. Grains dominated by carbon and/or organic matter (CHON grains) represent approx. 22% of the total population of measured cometary dust particles. They, usually contain a minor abundance of rock-forming elements as well. Grains having organic material are relatively more abundant in the vicinity of the nucleus than in the outer regions of the coma, which suggests decomposition of the organics in the coma environment. The majority of comet Halley organic particles are multicomponent mixtures of carbon phases and organic compounds. Possibly, the cometary CHON grains may be related to kerogen material of an interstellar origin in carbonaceous meteorites. Pure carbon grains, hydrocarbons and polymers of cyanopolyynes, and multi-carbon monoxides are present in cometary dust as compositionally simple and distinctive components among a variety of others. There is no clear evidence of significant presence of pure formaldehyde or HCN polymers in Halley dust particles. The diversity of types of cometary organic compounds is consistent with the inter-stellar dust model of comets and probably reflects differences in composition of precursor dust. Preservation of this heterogeneity among submicron particles suggest the gentle formation of cometary, nucleus by aggregation of interstellar dust in the protosolar nebula without complete mixing or chemical homogenization at the submicron level.
Document ID
19970015337
Document Type
Reprint (Version printed in journal)
Authors
Fomenkova, M. N.
(NASA Ames Research Center Moffett Field, CA United States)
Chang, S.
(NASA Ames Research Center Moffett Field, CA United States)
Mukhin, L. M.
(Institute of Space Research Moscow, USSR)
Date Acquired
August 17, 2013
Publication Date
July 20, 1994
Publication Information
Publication: Geochimica et Cosmochimica Acta
Volume: 58
Issue: 20
ISSN: 0016-7037
Subject Category
Astrophysics
Report/Patent Number
NASA-TM-112666
NAS 1.15:112666
Distribution Limits
Public
Copyright
Public Use Permitted.
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