2GPa以上で安定したメタン水合物であり,タイタンの大気中のメタンの源である
J S Loveday1, R J Nelmes, M Guthrie
1Department of Physics and Astronomy, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JZ, UK. J.Loveday@ed.ac.uk
Nature
|April 5, 2001
まとめ
メタン水素は,以前の仮定とは異なり,タイタンの内部で高圧下でも安定したままでした. この安定性は,月の大気中のメタンを説明し,その氷のマントルの内部にクラトラート層があることを示唆しています.
科学分野:
- 惑星科学は惑星科学である.
- 地質化学 地質化学
- マテリアルサイエンス 材料科学
背景:
- メタン水素は,外惑星とその衛星の形成を理解するために不可欠です.
- 以前のモデルでは,1〜2GPaでのメタン水素解離を想定しており,タイタンの大気中のメタンに課題を投げかけていた.
- タイタンの大気中のメタンの存在は,その内部にある安定した源を必要とします.
研究 の 目的:
- 惑星形成に関連する高圧下でのメタン水素の熱力学的振る舞いを調査する.
- タイタンの内部で見られる条件下でメタン水素相の安定性を決定するために.
- タイタンの観測された大気中のメタンをその形成の歴史と調和させるため.
主な方法:
- ニュートロン difraktion 研究. ニュートロン difraktion 研究.
- シンクロトロンX線 difraktion研究. シンクロトロンX線 difraktion研究.
- 10GPaまでのメタン水合物の熱力学分析.
主要な成果:
- メタン水素は,約1〜2GPaで構造変化を起こします.
- 新しい水素相は,少なくとも10GPaまでの圧力で安定しています.
- これらの発見は,メタン水素酸の推定解離圧力と矛盾しています.
結論:
- タイタンの核の原始的なメタンは,微分化中に安定した水素相にとどまった可能性が高い.
- 厚さ約100kmのメタンクラスレート層は,タイタンの氷のマントルの中に存在している可能性がある.
- この安定したクラスラート層は,タイタンの大気中のメタンの補給のための妥当な源を提供します.
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