エンケラドスの表面下にある海からのEリングの氷粒に含まれるナトリウム塩
F Postberg1, S Kempf, J Schmidt
1Institut für Geowissenschaften, Universität Heidelberg, 69120 Heidelberg, Germany. frank.postberg@mpi-hd.mpg.de
Nature
|June 26, 2009
まとめ
土星のE環の粒子の分析により,高いナトリウム塩含有量が明らかになり,エンケラドスの存在が確認されました.
科学分野:
- 惑星科学:土星の衛星エンケラドスのEリング粒子の構成と起源を調査する.
背景:
- 土星の衛星エンケラドスは南極から羽根を放つので,潜在的に地下の海があることを示している.
- これらの羽根は,土星のE環の氷粒子の主要な源である.
- 以前の分析では,羽根粒子の有機的または状成分が示唆され,コアと水の相互作用を暗示していました.
研究 の 目的:
- エンケラドスの地下液体の水が今日も存在するかどうかを判断するためです.
- Eリングの粒子の化学組成を特定し,羽根の起源条件を推論する.
主な方法:
- Eリングの氷粒のインサイト分析.
- 塩の成分,特にナトリウム塩の識別と定量化.
- 観測された塩の量と推測されたpHをエンケラドスの海洋モデルと比較.
主要な成果:
- 塩酸ナトリウムが豊富なEリング粒子の集団 (質量0.5-2%) が特定されました.
- 塩の組成と推論された基本的なpHは,エンケラドスの海洋が岩石の核と相互作用するとの予測と密接に一致しています.
- 原子ナトリウムは羽ばたき蒸気には含まれないので,光学スペクトルには含まれない.
結論:
- Eリングの粒子の中のナトリウム塩の存在は,今日もエンケラドスから発生した液体の水柱の存在に強い証拠を提供している.
- これらの粒子の組成は,エンケラドスの地下海洋が岩石の核と相互作用しているという仮説を支持している.
- この発見は,エンケラドスの内部海洋と羽根生成の現在のモデルと一致しています.
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