Rapid accretion and early core formation on asteroids and the terrestrial planets from Hf-W chronometry
Rapid accretion and early core formation on asteroids and the terrestrial planets from Hf-W chronometry
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DOI：
10.1038/nature00982
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发表时间：
2002-08-29
期刊：
影响因子：
64.8
通讯作者：
Palme, H
中科院分区：
文献类型：
--
作者：
Kleine, T;Münker, C;Palme, H
行星形成和化学分化的时间尺度和机制可以利用短寿命同位素的放射性衰变来量化（1-10）。其中，hf -182到w -182的衰变非常适合于确定行星体核心形成的年代（1-5）。在较早的一项研究中，地幔的W同位素组成(1)被用来推断地核形成较晚(1)（大于或等于太阳系开始后的6000万年），并且吸积是一个漫长的过程（11,12）。然而，对Hf-W数据的正确解释取决于对太阳系中Hf-182初始丰度的准确了解和球粒陨石的w同位素组成。在这里，我们报告了碳质和氢球粒陨石的Hf-W数据，这些数据导致吸积和核心形成的时间尺度与之前计算的结果有显著不同（1,3,5,11,12）。修正后的灶神星、火星和地球的年龄表明了快速的吸积，并表明核心形成的时间尺度随着行星体积的减小而减小。我们得出结论，类地行星的地核形成和月球的形成一定发生在太阳系生命的最初大约3000万年。
The timescales and mechanisms for the formation and chemical differentiation of the planets can be quantified using the radioactive decay of short-lived isotopes(1-10). Of these, the Hf-182-to-W-182 decay is ideally suited for dating core formation in planetary bodies(1-5). In an earlier study, the W isotope composition(1) of the Earth's mantle was used to infer that core formation was late(1) (greater than or equal to60 million years after the beginning of the Solar System) and that accretion was a protracted process(11,12). The correct interpretation of Hf-W data depends, however, on accurate knowledge of the initial abundance of Hf-182 in the Solar System and the Wisotope composition of chondritic meteorites. Here we report Hf-W data for carbonaceous and H chondrite meteorites that lead to timescales of accretion and core formation significantly different from those calculated previously(1,3,5,11,12). The revised ages for Vesta, Mars and Earth indicate rapid accretion, and show that the timescale for core formation decreases with decreasing size of the planet. We conclude that core formation in the terrestrial planets and the formation of the Moon must have occurred during the first similar to30 million years of the life of the Solar System.