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首页> 外文期刊>Geochemistry, geophysics, geosystems >Asteroid bombardment and the core of Theia as possible sources for the Earth's late veneer component
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Asteroid bombardment and the core of Theia as possible sources for the Earth's late veneer component

机译：小行星轰炸和Theia的核心可能是地球后期胶合板组件的来源

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The silicate Earth contains Pt-group elements in roughly chondritic relative ratios, but with absolute concentrations <1% chondrite. This veneer implies addition of chondrite-like material with 0.3-0.7% mass of the Earth's mantle or an equivalent planet-wide thickness of 5-20 km. The veneer thickness, 200-300 m, within the lunar crust and mantle is much less. One hypothesis is that the terrestrial veneer arrived after the moon-forming impact within a few large asteroids that happened to miss the smaller Moon. Alternatively, most of terrestrial veneer came from the core of the moon-forming impactor, Theia. The Moon then likely contains iron from Theia's core. Mass balances lend plausibility. The lunar core mass is approximate to 1.6 x 10(21) kg and the excess FeO component in the lunar mantle is 1.3-3.5 x 10(21) kg as Fe, totaling 3-5 x 10(21) kg or a few percent of Theia's core. This mass is comparable to the excess Fe of 2.3-10 x 10(21) kg in the Earth's mantle inferred from the veneer component. Chemically in this hypothesis, Fe metal from Theia's core entered the Moon-forming disk. H2O and Fe2O3 in the disk oxidized part of the Fe, leaving the lunar mantle near a Fe-FeO buffer. The remaining iron metal condensed, gathered Pt-group elements eventually into the lunar core. The silicate Moon is strongly depleted in Pt-group elements. In contrast, the Earth's mantle contained excess oxidants, H2O and Fe2O3, which quantitatively oxidized the admixed Fe from Theia's core, retaining Pt-group elements. In this hypothesis, asteroid impacts were relatively benign with approximate to 1 terrestrial event that left only thermophile survivors.
机译：硅酸盐地球含有大致呈软骨状相对比率的Pt基元素，但绝对浓度小于1％的球粒晶。这种单板意味着添加了类似球粒陨石的材料，其质量相当于地球地幔的0.3-0.7％，或者相当于全地球的厚度5-20 km。月球地壳和地幔中的单板厚度200-300 m少得多。一种假设是，地面饰面到达月球撞击少数几颗大型小行星后就碰巧遇到了较小的月亮。另外，大多数地面单板来自形成月球的撞击器Theia的核心。这样，月球很可能会包含蒂亚核心的铁。质量平衡使合理性得到提高。月球核心质量约为1.6 x 10（21）kg，月幔中过量的FeO成分为Fe的1.3-3.5 x 10（21）kg，总计3-5 x 10（21）kg或百分之几Theia的核心该质量相当于单板组件推断出的地幔中多余的Fe 2.3-10 x 10（21）kg。从化学假设出发，Theia核心的铁金属进入形成月球的盘中。圆盘中的H2O和Fe2O3氧化了部分Fe，使月球幔靠近Fe-FeO缓冲液。剩下的铁金属凝结成团，最终聚集到月球芯中。硅酸盐月亮中的铂族元素含量极低。相反，地球的地幔中含有过量的氧化剂H2O和Fe2O3，它们定量地氧化了Theia核心中混合的Fe，保留了Pt类元素。在此假设下，小行星撞击相对温和，大约有1次地面事件，仅留下嗜热幸存者。

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