时间学证据表明,月球要么年轻,要么没有全球性岩海洋
Lars E Borg1, James N Connelly, Maud Boyet
1Chemical Sciences Division, Lawrence Livermore National Laboratory, 7000 East Avenue L-231, Livermore, California 94550, USA. borg5@llnl.gov
Nature
|August 19, 2011
概括
月球上最古老的地岩石 - - 铁甲基岩 (FAN) 可能不是来自原始的岩海洋. 新的同位素约会表明,结晶年龄令人惊地年轻,这挑战了现有的月球形成理论.
科学领域:
- 行星科学 行星科学
- 地质化学 地质化学
- 同位素地质年代学 同位素地质年代学
背景情况:
- 理论上,包括月球在内的行星差异化始于岩海洋固化.
- 铁色岩石 (Ferroan anorthosites,简称FANs) 被认为是月球表面的主要岩石,是在 magma海洋结晶的后期阶段形成的.
- 之前试图测定FAN的日期,由于同位素不相容,导致了模糊的结果.
研究的目的:
- 为了准确地确定铁甲酸 (FAN) 的结晶年龄 60025.
- 重新评估目前关于月球地形成的岩海洋假设.
主要方法:
- 利用改进的同位素技术来精确确定年龄.
- 应用的 (207) Pb - 206) Pb, (147) Sm - 143 Nd,和 (146) Sm - 142 Nd同位素系统.
主要成果:
- 确定FAN 60025的结晶年龄为4360±300万年.
- 这个年龄比以前估计的初级月球地岩石要年轻得多.
结论:
- 这个年轻的年龄挑战了长期以来的假设,即FANs是来自原始的月球岩海洋的浮动积累.
- 其他模型,如连续性岩,可能是造成月球地的大部分原因.
- 这一发现需要对月球形成和进化时间表进行修订.
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