酸素のイソトープと月を形成した巨大な衝突
U Wiechert1, A N Halliday, D C Lee
1Institute for Isotope Geology and Mineral Resources, Department of Earth Sciences, ETH Zentrum, Sonneggstrasse 5, 8092 Zürich, Switzerland. wiechert@erdw.ethz.ch
まとめ
月面の岩は,地球と同一の酸素同位体比を示し,巨大衝突の仮説を裏付けている. これは,原地球とインパクターテイアが類似した物質から生じたことを示しており,イソトープの違いを生む月のインパクトの証拠はありません.
科学分野:
- 宇宙化学 (コスモケミストリー)
- 惑星科学は惑星科学である.
- 地質化学 地質化学
背景:
- 巨大衝突仮説は,火星サイズの天体 (テイア) が原地球と衝突した後の残骸から月が形成されたことを示唆している.
- 月面のサンプルの酸素同位体は,月の起源と地球との関係に関する重要な洞察を提供します.
研究 の 目的:
- 月面のサンプルの酸素同位体 (16O, 17O, 18O) を正確に測定する.
- 月の酸素同位体組成を地上の値と比較して惑星形成モデルをテストする.
主な方法:
- 酸素同位体分析のために高精度のレーザー化技術を使用した.
- アポロミッション11,12,15,16,17号からの月面サンプル31個を分析した.
主要な成果:
- すべての分析された月面サンプルには,単一の質量依存分割線に属する酸素同位体組成が示されました.
- この線は,実験上の不確実性において,地上の分割線と区別することができなかった.
- 月面衝突によって引き起こされる月の同位体異質性の証拠は見つかりませんでした.
結論:
- 同様の酸素同位体シグネチャは巨大衝突モデルを支持し,原地球とテイアが共通の同位体組成を共有していたことを示唆しています.
- この共通の組成は,両体が類似の太陽の中心距離で形成されたことを示唆している.
- 月面衝突は,月面での酸素同位体変動の重要な源ではないようです.
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