| Project/Area Number |
15340194
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Geochemistry/Astrochemistry
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| Research Institution | National Science Museum |
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Principal Investigator |
YONEDA Shigekazu National Science Museum, Dept.of Science and Engineering, Senior Curator, 理工学研究部, 主任研究官 (60210788)
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| Co-Investigator(Kenkyū-buntansha) |
HIDAKA Hiroshi Hiroshima University, Faculty of Science, Professor, 大学院・理学研究科, 教授 (10208770)
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| Project Period (FY) |
2003 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥13,400,000 (Direct Cost: ¥13,400,000)
Fiscal Year 2005: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 2004: ¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2003: ¥8,400,000 (Direct Cost: ¥8,400,000)
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| Keywords | extinct nuclide / cesium-135 / meteorite / barium / isotopic abundance / age determination / formation of the solar system / early solar nebula / Orgueil / Murray / Mighei / Cs-135 / Ba / NWA801 / Kainsaz / Karoonda / Murchison / Sayama / Juvinas |
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| Research Abstract |
Extinct nuclides are radioactive nuclides which existed in the early solar system but decayed thoroughly due to their short half lives. However, their daughter nuclides are often detected as isotopic anomalies in primitive meteorites such as carbonaceous meteorites, and this can be used for chronology of the early solar system. We have found the Ba isotopic anomaly in the Beardsley meteorite and suggested that this is due to the extinct nuclide Cs-135 (half life 2.3Ma). In the current study, we try to establish the existence of Cs-135 and apply it for chronology in the early solar system
We measured the barium isotopic abundances in various meteorites, especially carbonaceous chondrites. Most carbonaceous chondrites of CI, CM, CR and CV groups show the Ba-135 and Ba-137 isotopic anomalies simultaneously, which imply that these anomalies are mainly due to nucleosynthesis of s-process and/or r-process. On the other hand, thermally-altered CK group carbonaceous chondrites and achondrites do not show any significant anomalies. Their Ba isotopic abundances could be homogenized at their parent bodies.
Part of the r-process components in the barium isotopic anomalies of CM chondrites could be corrected and the Cs-135 chronology suggests the formation age of 7 (+5/-2) Ma. This age is shorter than the formation age of CI carbonates by Mn-53 extinct nuclide chronology and may suggest the re-distribution of Ba at the parent bodies.
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