Estimation of the existence period of water in the early solar system by the precise barium isotopic ratio measurements of meteorites

2017 Fiscal Year Final Research Report

• Project/Area Number: 15K05356
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Geochemistry/Cosmochemistry
• Research Institution: National Museum of Nature and Science, Tokyo
• Principal Investigator: Yoneda Shigekazu 独立行政法人国立科学博物館, 理工学研究部, グループ長 (60210788)
• Co-Investigator(Kenkyū-buntansha): 日高 洋 名古屋大学, 環境学研究科, 教授 (10208770)
• Project Period (FY): 2015-04-01 – 2018-03-31
• Keywords: 同位体・放射年代 / 隕石 / バリウム / ダブルスパイク法 / 太陽系初期

Outline of Final Research Achievements

Evidence of the existence of water in the early solar system remains in meteorites. In this study, the isotopic ratios of barium in meteorites were precisely measured, and the age determination was examined by detecting the isotopic anomalies of Ba-135 due to the extinct nuclide Cs-135. About 10-40 ppm isotopic measurement accuracy was obtained with the standard solution, and the double spike method was studied using the Ba-130 and other concentrated isotopes. In Tagish Lake carbonaceous chondrites, significant isotopic anomalies were observed in Ba-135 and Ba-137. These are thought to be brought to the primitive solar nebula with presolar grains and are retained heterogeneously in meteorites. No correlation was found between the Cs/Ba ratio and the isotopic excess, hence it is presumed that cesium migrated due to the water at the early metamorphic process.

Free Research Field

宇宙化学、隕石学