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Title: Isotopic Evidence for Multi-stage Cosmic-ray Exposure Histories of Lunar Meteorites: Long Residence on the Moon and Short Transition to the Earth

Abstract

It is known that most lunar meteorites have complicated cosmic-ray exposure experiences on the Moon and in space. In this study, cosmic-ray irradiation histories of six lunar meteorites, Dhofar 489, Northwest Africa 032 (NWA 032), NWA 479, NWA 482, NWA 2995, and NWA 5000, were characterized from neutron-captured isotopic shifts of Sm and Gd, and from the abundances of long-lived cosmogenic radionuclides like {sup 10}Be, {sup 26}Al, {sup 36}Cl, and {sup 41}Ca. Sm and Gd isotopic data of all of six meteorites show significant isotopic shifts of {sup 149}Sm–{sup 150}Sm and {sup 157}Gd–{sup 158}Gd caused by accumulation of neutron capture reactions due to cosmic-ray irradiation, corresponding to the neutron fluences of (1.3–9.6) × 10{sup 16} n cm{sup −2}. In particular, very large Sm and Gd isotopic shifts of NWA 482 are over those of a lunar regolith 70002, having the largest isotopic shifts among the Apollo regolith samples, corresponding to cosmic-ray exposure duration over 800 million years in the lunar surface (2 π irradiation). Meanwhile, the concentrations of cosmogenic radionuclides for individual six meteorites show the short irradiation time less than one million years as their bodies in space (4 π irradiation). Our data also support the results of previous studies, revealingmore » that most of lunar meteorites have long exposure ages at shallow depths on the Moon and short transit times from the Moon to the Earth.« less

Authors:
;  [1];  [2];  [3]
  1. Department of Earth and Planetary Sciences, Nagoya University Nagoya 464-8601 (Japan)
  2. Space Sciences Laboratory, University of California, Berkeley, CA 94720-7450 (United States)
  3. Department of Science and Engineering, National Museum of Nature and Science Tsukuba 305-0005 (Japan)
Publication Date:
OSTI Identifier:
22666283
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astronomical Journal (Online); Journal Volume: 153; Journal Issue: 6; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ALUMINIUM 26; BERYLLIUM 10; BUILDUP; CALCIUM 41; CAPTURE; CHLORINE 36; COSMIC RADIATION; GADOLINIUM 157; GADOLINIUM 158; METEORITES; METEOROIDS; MOON; NEUTRON FLUENCE; NEUTRON REACTIONS; OVERBURDEN; SAMARIUM 149; SAMARIUM 150; SPECTRAL SHIFT

Citation Formats

Hidaka, Hiroshi, Sakuma, Keisuke, Nishiizumi, Kunihiko, and Yoneda, Shigekazu, E-mail: hidaka@eps.nagoya-u.ac.jp. Isotopic Evidence for Multi-stage Cosmic-ray Exposure Histories of Lunar Meteorites: Long Residence on the Moon and Short Transition to the Earth. United States: N. p., 2017. Web. doi:10.3847/1538-3881/AA7139.
Hidaka, Hiroshi, Sakuma, Keisuke, Nishiizumi, Kunihiko, & Yoneda, Shigekazu, E-mail: hidaka@eps.nagoya-u.ac.jp. Isotopic Evidence for Multi-stage Cosmic-ray Exposure Histories of Lunar Meteorites: Long Residence on the Moon and Short Transition to the Earth. United States. doi:10.3847/1538-3881/AA7139.
Hidaka, Hiroshi, Sakuma, Keisuke, Nishiizumi, Kunihiko, and Yoneda, Shigekazu, E-mail: hidaka@eps.nagoya-u.ac.jp. Thu . "Isotopic Evidence for Multi-stage Cosmic-ray Exposure Histories of Lunar Meteorites: Long Residence on the Moon and Short Transition to the Earth". United States. doi:10.3847/1538-3881/AA7139.
@article{osti_22666283,
title = {Isotopic Evidence for Multi-stage Cosmic-ray Exposure Histories of Lunar Meteorites: Long Residence on the Moon and Short Transition to the Earth},
author = {Hidaka, Hiroshi and Sakuma, Keisuke and Nishiizumi, Kunihiko and Yoneda, Shigekazu, E-mail: hidaka@eps.nagoya-u.ac.jp},
abstractNote = {It is known that most lunar meteorites have complicated cosmic-ray exposure experiences on the Moon and in space. In this study, cosmic-ray irradiation histories of six lunar meteorites, Dhofar 489, Northwest Africa 032 (NWA 032), NWA 479, NWA 482, NWA 2995, and NWA 5000, were characterized from neutron-captured isotopic shifts of Sm and Gd, and from the abundances of long-lived cosmogenic radionuclides like {sup 10}Be, {sup 26}Al, {sup 36}Cl, and {sup 41}Ca. Sm and Gd isotopic data of all of six meteorites show significant isotopic shifts of {sup 149}Sm–{sup 150}Sm and {sup 157}Gd–{sup 158}Gd caused by accumulation of neutron capture reactions due to cosmic-ray irradiation, corresponding to the neutron fluences of (1.3–9.6) × 10{sup 16} n cm{sup −2}. In particular, very large Sm and Gd isotopic shifts of NWA 482 are over those of a lunar regolith 70002, having the largest isotopic shifts among the Apollo regolith samples, corresponding to cosmic-ray exposure duration over 800 million years in the lunar surface (2 π irradiation). Meanwhile, the concentrations of cosmogenic radionuclides for individual six meteorites show the short irradiation time less than one million years as their bodies in space (4 π irradiation). Our data also support the results of previous studies, revealing that most of lunar meteorites have long exposure ages at shallow depths on the Moon and short transit times from the Moon to the Earth.},
doi = {10.3847/1538-3881/AA7139},
journal = {Astronomical Journal (Online)},
number = 6,
volume = 153,
place = {United States},
year = {Thu Jun 01 00:00:00 EDT 2017},
month = {Thu Jun 01 00:00:00 EDT 2017}
}