原惑星円盤の同位体進化と地球と月の構成要素
Martin Schiller1, Martin Bizzarro1, Vera Assis Fernandes2,3
1Centre for Star and Planet Formation and Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, DK-1350, Denmark.
Nature
|March 23, 2018
まとめ
太陽系内部のイソトープの変動は空間的な違いによるものではなく,原惑星円盤内のカルシウムイソトープの急速な変化によるものである. この急速な変化は 初期の太陽の質量増量と関連しており 惑星の形成と 地球と月のシステムの理解に影響を与えます
科学分野:
- 惑星科学
- 宇宙化学
- 同位体地化学
背景:
- 太陽系の物体における核合成同位体の変動は,隕石と惑星の遺伝関係を伝える.
- 以前の研究では,原惑星円盤の空間的異質性が示唆され,地球と月の構成要素は制限されませんでした.
研究 の 目的:
- 太陽系内部の核合成イソトープの変動の主な要因を調査する.
- カルシウムイソトープを用いて,地上の惑星と地球月系を再評価する.
主な方法:
- 隕石 (ウレイライト,アングライト),ヴェスタ,火星,地球における質量独立の48Ca/44Ca比の測定.
- 主体/惑星の質量とのカルシウム同位体組成の相関分析 (蓄積時間スケール).
- 普通のコンドライトのコンドルールにおけるカルシウム同位体の分析.
主要な成果:
- 太陽系内部のカルシウム同位体の変動は,空間的な異質性ではなく,主に原惑星円盤の固体の急速な変化によって引き起こされる.
- 質量独立の48Ca/44Ca比と蓄積時間スケールの間には正の相関関係がある.
- コンドルルは,初期の原始惑星円盤の素早い組成の変化を示し,同位体変動の全範囲を明らかにする.
結論:
- 地上の惑星形成領域におけるカルシウム同位体組成の長期進化が推論されている.
- 太陽系外部の物質が初期の太陽質量蓄積時に内部の円盤に混じり合うことが提案されている.
- このモデルは,月形成の衝突が遅い加熱体を含んだ場合,地球と月の同一のカルシウム同位体組成を予測している.
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