A colossal impact enriched Mars' mantle with noble metals
A colossal impact enriched Mars' mantle with noble metals
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DOI：
10.1002/2017gl074002
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发表时间：
2017-06-28
影响因子：
5.2
通讯作者：
Mojzsis, S. J.
中科院分区：
文献类型：
--
作者：
Brasser, R.;Mojzsis, S. J.
一旦类地行星基本完成组装，吸积留下的行星体继续进行轰击。火星地幔中高度亲铁元素(HSE)的丰度表明其晚期的吸积补充为0.8wt%；地球和月球分别获得了额外的0.7wt%和0.02wt%。地球/月球不成比例的高吸积率可以通过随机添加几个谷神星大小的优先瞄准地球的天体来解释。在这里，我们展示了火星后期的吸积预算也需要一个巨大的影响，其中一个看似合理的可见残留物是发射体二分法。在火星地幔中添加足够的HSE需要一个直径至少1200公里的冲击器，才能在大约4430 Ma之前撞击火星，当时地壳形成已经很好地进行了。因此，这种二分法可能是火星地壳最古老的地球物理特征之一。喷出的碎片可能是其卫星的来源材料。
Once the terrestrial planets had mostly completed their assembly, bombardment continued by planetesimals left over from accretion. Highly siderophile element (HSE) abundances in Mars' mantle imply that its late accretion supplement was 0.8wt %; Earth and the Moon obtained an additional 0.7wt % and 0.02wt %, respectively. The disproportionately high Earth/Moon accretion ratio is explicable by stochastic addition of a few remaining Ceres-sized bodies that preferentially targeted Earth. Here we show that Mars' late accretion budget also requires a colossal impact, a plausible visible remnant of which is the emispheric dichotomy. The addition of sufficient HSEs to the Martian mantle entails an impactor of at least 1200km in diameter to have struck Mars before similar to 4430Ma, by which time crust formation was well underway. Thus, the dichotomy could be one of the oldest geophysical features of the Martian crust. Ejected debris could be the source material for its satellites.