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Cosmic-ray exposure ages of the ordinary chondrites and their significance for parent body stratigraphyImproved exposure ages are derived for 201 H, 203 L, and 38 LL chondrites in an effort to understand the characteristics of the chondrite parent body. The Ne-21 exposure ages were calculated from literature values taking into account shielding differences, a trapped component and radiogenic He. The exposure age distributions show clear peaks at 4.5 and 20 million years for the H chondrites, while the Ls and LLs appear more as a continuous series of intermediate peaks which may be modeled by at least six peaks between 1 and 35 million years in the case of L chondrites. The observations that every petrological type occurs in each large peak and contain solar wind gases suggest that the parent bodies have been fragmented and reassembled into a megabreccia. The H meteorites are proposed to represent the surface layer of a body with a substantial, active regolith as indicated by the relatively high abundances of solar gases. The L chondrites, on the other hand, are attributed to a parent body that was fragmented by collision about 500 million years ago.
Document ID
19820033469
Document Type
Reprint (Version printed in journal)
Authors
Crabb, J. (Chicago, University Chicago, IL, United States)
Schultz, L. (Max-Planck-Institut fuer Chemie Mainz, Germany)
Date Acquired
August 10, 2013
Publication Date
November 1, 1981
Publication Information
Publication: Geochimica et Cosmochimica Acta
Volume: 45
Subject Category
LUNAR AND PLANETARY EXPLORATION
Funding Number(s)
CONTRACT_GRANT: NGL-14-001-010
Distribution Limits
Public
Copyright
Other