タギシュ湖の隕石の有機球:原太陽円盤の残骸
Keiko Nakamura-Messenger1, Scott Messenger, Lindsay P Keller
1Robert M. Walker Laboratory for Space Science, Astromaterials Research and Exploration Science Directorate, NASA Johnson Space Center, Houston, TX 77058, USA. keiko.nakamura-1@nasa.gov
まとめ
タギシュ湖の隕石の有機球体は,極端な同位体異常を明らかにしています. これらの発見は,彗星粒子に似た,冷たい,初期の太陽系環境で形成された地球外の有機物質を示唆しています.
科学分野:
- 宇宙化学 (コスモケミストリー)
- 天体生物学 アストロバイオロジー
- 惑星科学は惑星科学である.
背景:
- 隕石は,初期の太陽系の構成に関する重要な洞察を提供します.
- 隕石に含まれる有機物質は,プレバイオティック化学に関する手がかりを提供します.
研究 の 目的:
- タギシュ湖の隕石で発見された有機球体の起源と形成条件を調査する.
- 有機物質の同位体組成を決定し,その地球外の起源を理解する.
主な方法:
- 協調伝送電子顕微鏡 (TEM) と同位素測定.
- 有機球体における窒素-15から窒素-14とデュテリウムから水素の比率の分析.
主要な成果:
- 有機球体は,地上の値と比較して,窒素-15/窒素-14とデウテリウム/水素の比率が著しく上昇しています.
- 同位体異常は,極低温 (10~20K) で質量分化による形成を示している.
- 構成は彗星の炭素,水素,酸素,窒素 (CHON) 粒子に似ている.
結論:
- オーガニック・グローブルは,冷たい分子雲や外側のプロトソーラーディスクの粒子の上の光化学処理された氷の層として形成された可能性が高い.
- これらの発見は,耐火性の有機物質に加工されたプレソラー粒子が,初期の太陽系の重要な構成要素であったことを示唆しています.
- この研究は,彗星のような物質が太陽系の有機在庫に寄与したという仮説を支持する.
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