カッシーニのISS libration測定からのミマスの内部への制約

R Tajeddine¹, N Rambaux², V Lainey³

¹Department of Astronomy, Cornell University, Ithaca, NY 14853, USA. IMCCE-Observatoire de Paris, UMR 8028 du CNRS, UPMC, Université Lille 1, 77 Av. Denfert-Rochereau, 75014 Paris, France. Université Pierre et Marie Curie, UPMC - Paris VI, 4 Place Jussieu, 75005 Paris, France. tajeddine@astro.cornell.edu.

Science (New York, N.Y.)

|October 18, 2014

まとめ

土星の月であるミマスは,予測から逸脱する物理的な解読を示し,非水静的内部または地下海洋のいずれかを示唆しています. これらの発見は,氷の月の内部構造に関する新しい洞察を提供します.

科学分野:

惑星科学は惑星科学である.
天体物理学天体物理学
地質物理学地質物理学とは地質物理学です.

背景:

ほとんどの太陽系衛星は1:1のスピン軌道共鳴を示し,惑星に向かって恒常的な顔を示しています.
衛星の物理的な libra ations,または振動は,内部特性を明らかにすることができます.
土星の衛星ミマス (Mimas) は,衛星の内部を理解するための重要なターゲットです.

研究の目的:

ミマスの縦断的な物理的な強制リブラションを測定するために.
ミマスの内部構造を,リブラーションの振幅を分析することによって調査する.
ミマスの内部のモデルをテストし,水静的均衡と海洋の存在を含む.

主な方法:

カッシーニ画像科学サブシステム (ISS) の画像にステレオフォトグラムメトリが適用された.
ミマスの縦断的な物理的な強制リブラーション幅の測定.
観測された振幅を軌道動力学と内部モデルに基づく予測と比較.

主要な成果:

観測された配列振幅は,1つの重要な例外を除いて,予測とほぼ一致しました.
1つのリブラーションで測定された振幅は,水立平衡を仮定して予測された値の2倍でした.
この不一致は,ミマスの内部構造が単純な水立模型から逸脱していることを示している.

結論:

ミマスの内部構造は,かなり非水静的である可能性が高い.
また,ミマスは,厚い氷の殻の下にある実質的な内部海洋を持つ水静的内部を有している可能性があります.
ミマスのライブラリが,ミマスの内部構成と進化に決定的な制約を与える.

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