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Tridymite and maghemite formation in an Fe-SiO smokeGrains produced in porous Fe-SiO smoke are analyzed by means of electron microscopy to determine their crystallographical, morphological, and chemical properties. The nucleation of metal oxide condensates takes place as the vapor evolves in a condensation-flow apparatus, initially producing simple crystalline phases. Fe nucleation follows, and the subsequent heterogeneous nucleation of quenched mixed high-Fe silica grains exhibits associated Fe-depletion, eventually producing pure silica grains. The coalescence exhibited by the pure silica grains is compatible with the higher surface energy found in the pure silica phase. During coagulation the grains melt and anneal to a chemically pure mixture of alpha- and beta-tridymite, and the precipitation of amorphous silica material is observed. The settling of grains in evolving solar nebula is theorized to be related to the stickiness of this material, and maghemite is suggested to contribute to the Fe/Si fractionation in solar nebula.
Document ID
19910057751
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Rietmeijer, F. J. M.
(New Mexico, University Albuquerque, United States)
Nuth, J. A., III
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 15, 2013
Publication Date
January 1, 1991
Subject Category
Astrophysics
Meeting Information
Meeting: Lunar and Planetary Science Conference
Location: Houston, TX
Country: United States
Start Date: March 12, 1990
End Date: March 16, 1990
Accession Number
91A42374
Funding Number(s)
CONTRACT_GRANT: NAG9-160
Distribution Limits
Public
Copyright
Other

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