45億年前に再融解したので 月は古くなりました
Francis Nimmo1, Thorsten Kleine2, Alessandro Morbidelli3,4
1Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, CA, USA. fnimmo@ucsc.edu.
Nature
|December 18, 2024
まとめ
月は太陽系が形成された直後に形成され,その年齢は軌道の変化による後の再融解によって再設定された. これは月の岩石の年代付けと月の構成の不一致を説明します.
科学分野:
- 惑星科学
- 地質年代学
- 月科学
背景:
- 月の形成は巨大衝突によるものと考えられていますが,月の岩石やジルコンの年代が異なるため,その正確な年齢は議論されています.
- 異なるサンプルタイプに基づいて,月の年齢は4350億年から4510億年前と推定されています.
研究 の 目的:
- 月の形成年齢の推定における不一致を 調和させるため
- 軌道進化と再融解を組み込んだ 月の歴史の新モデルを提案する.
主な方法:
- 月の全岩のサンプルとジルコンの粒子の年齢データを分析した.
- 月がラプラスの平面を通過する際の潮加熱の影響をモデル化している.
- 月面のサンプル年齢を 再融解の状況で再解釈する
主要な成果:
- 4.35億年前の月面岩の年齢とジルコンの年齢のピークは,最初の結晶化ではなく,重要な再融解のイベントを示しています.
- 軌道進化の過程で 潮による加熱が 月面のサンプルの大部分の年齢をリセットしたようです
- この再融解現象は 月の形状と 希少で古いジルコンの存在を説明します
結論:
- 月は太陽系の歴史の初期に 数千万年以内に形成されたと考えられます
- 軌道ダイナミクスによって引き起こされた 再融解は 月面サンプルの大部分の年齢をリセットしました
- この新しいパラダイムは,年齢の不一致を解決し,衝突盆の数が少ないことを説明し,月の核の組成を説明します.
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