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ID 29249
file
creator
Yoneda, Shigekazu
subject
cosmic ray exposure
Meteorite
neutron capture
Samarium
gadolinium
NDC
Astronomy. Space sciences
abstract
Sm-150/Sm-149 and Gd-158/Gd-157 isotopic shifts in extraterrestrial materials provide evidence of the occurrence of neutron capture reactions caused by the interaction of cosmic rays with the surface of the materials. The Sm and Gd isotopic shifts of chemical leachates from the Kapoeta meteorite, known as a solar-gas-rich meteorite, show a clear neutron capture record corresponding to the neutron fluence up to 9.0 x 10(15) n cm(-2). The intensities of the neutron fluences of two fractions from Kapoeta significantly exceed what is expected from the time for cosmic ray irradiation during the transit to Earth. Furthermore, the combination of Sm and Gd isotopic shifts, defined as epsilon(Sm)/epsilon(Gd) to understand the neutron energy spectrum, shows a different neutron irradiation environment for certain components of Kapoeta (epsilon(Sm)/epsilon(Gd) = 1.9 +/- 0.5, and 1.9 +/- 0.7) from those of other meteorites and lunar samples (epsilon(Sm)/epsilon(Gd) = 0.4-0.9). The isotopic data of Sm and Gd from Kapoeta suggest the irradiation of non-thermalized neutrons with the energies over 1 eV from the early Sun.
journal title
Earth and Planetary Science Letters
volume
Volume 28
issue
Issue 1-2
start page
173
end page
178
date of issued
2009-07-30
publisher
Elsevier Science Bv
issn
0012-821X
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) 2009 Elsevier B.V.
relation url
department
Graduate School of Science