オスミウムイソトープは,原始的なコンドライトにおけるsプロセスキャリアの証拠である
A D Brandon1, M Humayun, I S Puchtel
1NASA Johnson Space Center, Mail Stop KR, Houston, TX 77058, USA. alan.d.brandon1@jsc.nasa.gov
まとめ
コンドライトのオスミウム同位体異常は,特定の核合成部位からの不溶性キャリア (Os(i)) を明らかにする. メタモルフィズムは,このキャリアを破壊し,加工された隕石の同位体の均質性をもたらしました.
科学分野:
- 宇宙化学 (コスモケミストリー)
- イソトープ地球化学 イソトープ地球化学
- 惑星科学は惑星科学である.
背景:
- コンドライト,原始的な隕石は,初期の太陽系物質を保存しています.
- オスミウム (Os) のイソトープは,恒星の核合成と隕石形成に関する洞察を提供します.
- プレソラー粒子は,地球外の同位体シグネチャーを運ぶものである.
研究 の 目的:
- 原始的な隕石におけるオスミウム同位体異常の起源と運搬者を調査する.
- オスミウムの同位体組成に対する変異過程の影響を決定する.
- プレソラーOSの責任であるsプロセス核合成の条件を制約する.
主な方法:
- オスミウムの化学抽出は,不均衡および変形した大量コンドライトから行う.
- オスミウムの同位体の高精度測定.
- イソトープ組成を比較して,プレソラーキャリアと変形効果を特定する.
主要な成果:
- 不均衡なコンドライトのオスミウムは,不溶性S-プロセスキャリア (Os(i)) に起因する同位体異常を示している.
- メタモルフィズムにより,Os ((i)) キャリアが効果的に破壊され,メタモルフィスされたコンドライトにおけるオスミウムの同位体の均質化が生じた.
- Os(i) の同位体組成は,平均的な太陽系条件よりも高い中性子密度を持つs-プロセスサイトで形成されることを示唆しています.
結論:
- Os ((i) キャリアは,特定の恒星環境から発生した独特のプレソーラー成分を表しています.
- メタモルフィズムは,初期の太陽星雲におけるプレソーラー物質の処理と均質化において決定的な役割を果たしました.
- オスミウムイソトープの異常は,核合成と隕石の進化を理解するための敏感なトレーサーとして機能します.
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