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急速に回転する地球から月を作り出す:巨大な衝突に続いて,共鳴回転が起こります
1Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138, USA. cuk@eps.harvard.edu
Science (New York, N.Y.)
|October 19, 2012
まとめ
素早く回転する原地球への巨大衝突は,月の地球のような組成を説明することができます. より速い初期の地球・月系は,現在の状態に到達するために角運動量を落としました.
科学分野:
- 惑星科学は惑星科学である.
- 地質化学 地質化学
- 天体物理学 天体物理学
背景:
- 地球と月の同一の同位体成分は,共通の起源を示唆しています.
- 支配的な巨大衝突仮説は,シミュレーションが示すように,ほとんどの物質は衝撃物質から発生すべきであり,月の同位体相似性を説明するのに苦労しています.
- 以前のモデルでは,地球質量の惑星が収縮すると予想されるよりも,衝突後の角度モメンタムが低いと仮定していた.
研究 の 目的:
- 素早く回転する初期の地球が,月の形成モデルにおける同位体の不一致を解決できるかどうかを調査する.
- 初期の地球・月系における角運動量進化のメカニズムを探求する.
主な方法:
- 急速に回転する原地球への巨大衝突のコンピューターシミュレーション.
- 初期の地球・月系における角運動量の進化をモデリングする.
主要な成果:
- シミュレーションは,高速に回転する原地球への衝撃が,主に地球のマントルから月を形成する円盤を生成することを示しています.
- より高い初期 Momentum angular momentumにより,初期の地球-月系は余剰 angular momentum を失うことが可能になった.
- 太陽との軌道共鳴は,角運動量損失の妥当なメカニズムとして特定されています.
結論:
- 早く回転した初期の地球は,地球のような同位体シグネチャーを持つ月を形成する鍵です.
- 初期の地球・月系は,おそらくより高い角度運動量を持っていたが,その後,自然過程によって減少し,現在の状態に匹敵した.
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