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Noble gas concentrations and cosmic ray exposure ages of eight recently fallen chondritesAbundances and isotopic compositions of He, Ne, Ar, and Xe have been measured in eight recently fallen chondrites. Ratios of concentrations of cosmic ray-produced He-3, Ne-21, Ne-22, and Ar-38 indicate that all eight samples experienced less than average cosmic ray shielding. He-3 and Ne-21 exposure ages were calculated using shielding corrected chondritic production rates and the measured Ne-22/Ne-21. Exposure ages calculated from Na-22/Ne-22 and Al-26/Ne-21 ratios and constant relative production rates show a bias between the two ages due to variations in Na-22/Al-26. Arguments are presented that this bias is due to irradiation hardness differences, and therefore the use of constant values for both the Na-22/Ne-22 and Al-26/Ne-21 production ratios is not permitted.
Document ID
19740028332
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Bogard, D. D.
Reynolds, M. A.
(NASA Johnson Space Center Houston, Tex., United States)
Simms, L. A.
(NASA Johnson Space Center; Northrop Services, Inc. Houston, Tex., United States)
Date Acquired
August 7, 2013
Publication Date
November 1, 1973
Publication Information
Publication: Geochimica et Cosmochimica Acta
Volume: 37
Subject Category
Space Radiation
Accession Number
74A11082
Distribution Limits
Public
Copyright
Other

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