月面衝突盆地の非対称な分布は,ターゲット特性の変動によって引き起こされる

Katarina Miljkovićć¹, Mark A Wieczorek, Gareth S Collins

¹Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, Case 7011, Lamarck A, 5, 35 rue Hélène Brion, 75205 Paris cedex 13, France.

Science (New York, N.Y.)

|November 9, 2013

まとめ

月面衝突盆は,より高い温度のために,より冷たい裏側よりも,より暖かい近側でより大きい. この発見は,月の衝突盆の大きさ分布が,初期の太陽系爆撃の均一な記録ではないことを示唆しています.

科学分野:

惑星科学惑星科学
月面地質学月面地質学
インパクトクラテリング (インパクトクラテリング)

背景:

NASAのGravity Recovery and Interior Laboratory (GRAIL) ミッションは,月の地殻の厚さの地図を提供した.
GRAILのデータは,月面の近側と裏側との間の大きな衝突盆地における非対称性を明らかにした.
月面の近辺は,月面の裏側と比較して,熱を生成する元素の濃度が高く,火山活動が持続している.

研究の目的:

月面衝突盆地形成に対する熱変動の影響を調査する.
月面の近側と裏側との温度差が衝突クレーターの大きさに影響するかどうかを判断する.
初期の太陽系爆撃における月面衝突盆の大きさの分布の代表性を再評価する.

主な方法:

iSALE-2Dの水コードを使用して,様々な熱条件下で衝突盆の形成をシミュレートしました.
モデル化されたインパクトは,より熱い近側アナログと,より冷たい遠側アナログの月の地殻と上層マントルの両方に発生します.
近側と裏側条件を表すシミュレーションから得られた盆地直径を比較した.

主要な成果:

シミュレーションでは,より暑い近辺のアナログ形成盆地の衝撃が,より冷たい遠辺のアナログの衝撃の2倍の直径であることを示しました.
月面の近側と裏側との間の熱グラデントは,衝撃盆地形態学に大きな影響を及ぼします.
盆地サイズ分布の明確な違いは,半球に基づいて予測されています.

結論:

月面の近側と裏側との間の熱的非対称性は,衝突盆の大きさを制御する重要な要因です.
月面衝突盆の大きさは,初期の太陽系内部の衝突の歴史の均一なプロキシではありません.
将来の研究では,月の衝突記録を解釈する際に半球の熱変動を考慮する必要があります.

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