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月の高エネルギー巨大衝突の起源のカリウム同位体証拠
Kun Wang1,2, Stein B Jacobsen1
1Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, Massachusetts 02138, USA.
Nature
|September 13, 2016
まとめ
月の岩は重量のカリウムイソトープに富み 月形成の巨大衝突モデルを裏付けている この発見は,地球と月のシステムの起源と初期の惑星の条件に関する理論を洗練するのに役立ちます.
科学分野:
- 惑星科学
- 地化学
- 同位体地化学
背景:
- 地球と月のシステムは 独特の化学的および同位体特性を持っています
- カリウムのような 揮発性元素の減少は 重要な形成イベントを示唆しています
- 以前の研究では,月石が高濃度のカリウム同位体で富むために揮発性損失が予想されていましたが,これは未確認でした.
研究 の 目的:
- 地球,月,そして隕石のサンプルにおける カリウムの同位体組成を調べる
- 正確な同位体データを用いて 月形成モデルをテストする
- 月の形成条件のための"古気圧計"としてのカリウムイソトープを確立する.
主な方法:
- カリウム (K) 同位体の高精度分析
- 月,地,コンドリート隕石のサンプル間の同位体シグネチャーの比較.
- K同位体制約に対する月形成のダイナミックモデルの評価.
主要な成果:
- 月岩は,地球とコンドライトと比較して重いカリウムイソトープの濃度 (約0.4千分) を示しています.
- この濃縮は,10バーを超える圧力の大量シリケート地蒸気の不完全な凝縮によって説明される.
- 観測されたK同位体の分割は,低エネルギー円盤均衡モデルと矛盾しているが,高エネルギー巨大衝突モデルを支持している.
結論:
- 月の形成の巨大衝突モデルは,新しい高精度のカリウム同位体データによって支持されています.
- カリウム同位体データは,月形成の出来事を理解するために重要な制約を提供します.
- ポタシウム同位体分析は,惑星形成の過程で物理的条件を決定する貴重なツールとして役立つ.
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