地球地幔中的高度 siderophile 元素作为月球形成撞击的时钟
Seth A Jacobson1, Alessandro Morbidelli2, Sean N Raymond3
11] Observatoire de la Côte d'Azur, Laboratoire Lagrange, Boulevard de l'Observatoire, BP 4229, 06304 Nice Cedex 4, France [2] Universität Bayreuth, Bayerisches Geoinstitut, 95440 Bayreuth, Germany.
Nature
|April 4, 2014
概括
月球形成的巨大撞击发生在太阳系形成后的4000万年以后.
科学领域:
- 行星科学 行星科学
- 地质化学 地质化学
- 天体物理学 天体物理学
背景情况:
- 月球形成的巨大撞击对地球的核心形成和地幔演变至关重要.
- 这个事件的日期是具有挑战性的,建议的年龄在太阳系凝结后的3000万年至1亿年之间.
- 之前的模型在月球形成撞击的精确时间上缺乏共识.
研究的目的:
- 为了精确月球形成的巨大撞击事件的年龄.
- 为了建立巨大的撞击时间和晚期积累之间的强有力的关系.
- 用地化学证据来限制月球形成事件的时间.
主要方法:
- 利用N体模拟来模拟陆地行星形成场景 (古典和大塔克).
- 研究了最后一次巨大撞击的时间和随后的晚期积聚质量之间的相关性.
- 分析了地球地幔中的高度 siderophile 元素 (HSE) 度,以限制晚期积聚质量和推断撞击时间.
主要成果:
- 在99.9%的可信度水平下,排除了凝结后400万年或之前的月球形成.
- 证明了巨型撞击延迟和晚期积聚质量之间的可预测的反向关系.
- 根据HSE的丰度,在凝结后确定月球形成年龄为95±3200万年.
结论:
- 月球形成的撞击发生在太阳系凝结后的4000万年之后.
- 地球地幔中的HSE丰富性为确定月球形成事件的年代提供了一个强大的时钟.
- 即使考虑HSE记录中的潜在复杂性,同位素约束也支持月球形成的晚期时间.
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