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ID 15029
file
creator
Yoneda, Shigekazu
Marti, Kurt
NDC
Astronomy. Space sciences
abstract
Enstatite achondrites (aubrites) when compared to other stone meteorites have unusually long cosmic-ray exposure (CRE) ages. We report here the 150Sm/149Sm and 158Gd/157Gd ratios in six different structural phases, i.e., light and dark (shocked) grains and in matrix materials of Pesyanoe, in three different fragments from Pena Blanca Spring, and in one from Norton County, Shallowater, and Khor Temiki, to investigate the regolith history on the aubrite parent body. The results from phases components of Pesyanoe confirm earlier reported evidence for regolith irradiation of several aubrites. The inferred neutron fluences for six Pesyanoe separates vary between (2.13 and 2.82) × 1016 n cm-2. The fluences also significantly exceed those expected from cosmic-ray irradiation during transit to Earth and approach those observed in the lunar regolith. These observations confirm that the brecciated Pesyanoe meteorite, which contains solar wind (SW) gases only in dark phases, was processed in a regolith and that structural phases were differentially irradiated before compaction. On the other hand, in some aubrites (Mt. Egerton, Shallowater, Pena Blanca Spring, Norton County) neutron capture effects may entirely be due to space irradiation.
journal title
Geochimica et Cosmochimica Acta
volume
Volume 70
issue
Issue 13
start page
3449
end page
3456
date of issued
2006-07
publisher
Elsevier Inc.
issn
0016-7037
ncid
publisher doi
language
eng
nii type
Journal Article
HU type
Journal Articles
DCMI type
text
format
application/pdf
text version
author
rights
Copyright (c) 2006 Elsevier Inc.
relation is version of URL
http://dx.doi.org/10.1016/j.gca.2006.04.009
department
Graduate School of Science