火星半球の二分論に対する衝突起源の影響

F Nimmo¹, S D Hart, D G Korycansky

¹Department of Earth and Planetary Sciences, University of California, Santa Cruz, 1156 High Street, Santa Cruz, California 95064, USA. fnimmo@es.ucsc.edu

Nature

|June 27, 2008

まとめ

巨大な衝突は,火星の半球二分法を説明し,地殻の下部とより薄い地殻を生み出します. このインパクトモデルは,反足の磁場減少と北の低地地地殻の融解の起源も説明しています.

科学分野:

惑星科学は惑星科学である.
地質物理学地質物理学とは地質物理学です.
インパクトクラテリング (インパクトクラテリング)

背景:

半球間の対照的な地殻の厚さと高さによって特徴づけられる火星半球二分法は,長年にわたる惑星科学の謎のままである.
ダイコトミーの形成に関する既存の仮説には,コンベクションなどの内部プロセスや,巨大衝突などの外部要因が含まれています.

研究の目的:

火星半球二分論の巨大衝突仮説を定量的にテストするために.
単一の衝突イベントが,火星の二分論の複数の観測された特徴を説明できるかどうかを調査する.

主な方法:

高解像度,二次元,軸対称のヒドロコードを使用して,初期の火星の垂直衝突をシミュレートしました.
火星の地質学史に関連する一連の衝突パラメータをモデル化しました.

主要な成果:

衝撃モデルでは,観測された二分法に一致する地殻の穴を成功裏に発掘しました.
衝突アンチポードの地殻の破壊は,観測された磁場強度の減少と相関しています.
北部の低地における衝突による融解は,深層で枯渇したマントルの源泉から発生すると予測されています.

結論:

巨大な衝突イベントは,火星半球の二分論の実行可能な説明を提供します.
衝突モデルは,対極磁場異常の観測と,火星の隕石 (シェルゴッタイト) の組成と一致しています.
ディコトミー形成は,火星の増殖から約1億年後に起こったと推定されています.

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