NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
The solar nebula redox state as recorded by the most reduced chondrules of five primitive chondritesMafic minerals in the most reduced chondrules of five primitive meteorites were analyzed with an electron microprobe to determine the lower limit on their FeO contents. The accuracy obtained was + or - 0.01 weight percent FeO. The thermodynamic relationship between mole fraction FeSiO3 and pO2 of the ambient nebular gas at the time of mineral equilibration was established, and was used to infer the local O/H ratio of the nebular gas during chondrule formation. The lowest ferrosilite compositions reflected equilibration at 1500 K with a gas 2-18 times more oxidizing than a gas of solar composition. Olivines in low-FeO unequilibrated ordinary chondrites (UOC) chondrules are uniformly more FeO-rich than coexisting pyroxenes. This discrepancy suggests that a significant change in the O/H ratio of the nebular gas occurred between the time of olivine and pyroxene crystallization in the region of the nebula where UOCs formed. Mineral compositions in the chondrules of two C2 chondrites studied suggest they formed in a more homogeneous region of the nebula than the UOCs.
Document ID
19870025014
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Johnson, M. C.
(Harvard-Smithsonian Center for Astrophysics Cambridge, MA, United States)
Date Acquired
August 13, 2013
Publication Date
July 1, 1986
Publication Information
Publication: Geochimica et Cosmochimica Acta
Volume: 50
ISSN: 0016-7037
Subject Category
Lunar And Planetary Exploration
Accession Number
87A12288
Funding Number(s)
CONTRACT_GRANT: NAG9-28
Distribution Limits
Public
Copyright
Other

Available Downloads

There are no available downloads for this record.
No Preview Available