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arXiv 1708.08718astro-ph.EP
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最像地球的行星的元素丰度（不含丰度）

The Elemental Abundances (with Uncertainties) of the Most Earth-like Planet

Haiyang S. Wang, Charles H. Lineweaver, Trevor R. Ireland

备注：
24 pages, 8 figures and 5 tables; Accepted by Icarus on 21 August 2017, in press. doi.org/10.1016/j.icarus.2017.08.024
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摘要：

首先，地球以及太阳系中的其他岩石行星和围绕其他恒星运行的岩石系外行星都是恒星星云的耐火碎片，它们是由恒星星云形成的。为了根据恒星宿主的元素丰度来估计岩石系外行星的化学成分，我们需要更好地了解产生地球的脱挥发分作用。为了量化地球、太阳和太阳系中其他天体之间的化学关系，需要地球本体的元素丰度。将地球的成分与其他天体的成分进行比较的关键是确定整体成分，并对不确定性作出适当的估计。在这里，我们提出了一致性估计（与不确定性）的散装地球的元素丰度，可用于此类研究。首先，我们编译，合并和重新规范化的原始地幔（PM）和核心的异质文献值的一个大集合。然后，我们整合地球的标准径向密度分布，并将其重新归一化为当前对地球质量的最佳估计。使用i）密度分布，ii）核幔边界和iii）内核边界中的不确定性的估计，我们采用标准误差传播来获得$32.5 \pm 0.3$重量%的内核质量分数。我们的散装地球丰度是我们的和谐核心丰度和和谐PM丰度的加权和。我们的一致性估计的镁，锡，溴，硼，镉和Be的丰度显着低于以前的估计散装地球。我们对Na、K、Cl、Zn、Sr、F、Ga、Rb、Nb、Gd、Ta、He、Ar和Kr丰度的一致性估计值明显较高。我们的元素丰度的不确定性有效地校准了各种地球化学和地球物理假设下标准地球模型之间未解决的差异。

英文摘要：

To first order, the Earth as well as other rocky planets in the Solar System and rocky exoplanets orbiting other stars, are refractory pieces of the stellar nebula out of which they formed. To estimate the chemical composition of rocky exoplanets based on their stellar hosts' elemental abundances, we need a better understanding of the devolatilization that produced the Earth. To quantify the chemical relationships between the Earth, the Sun and other bodies in the Solar System, the elemental abundances of the bulk Earth are required. The key to comparing Earth's composition with those of other objects is to have a determination of the bulk composition with an appropriate estimate of uncertainties. Here we present concordance estimates (with uncertainties) of the elemental abundances of the bulk Earth, which can be used in such studies. First we compile, combine and renormalize a large set of heterogeneous literature values of the primitive mantle (PM) and of the core. We then integrate standard radial density profiles of the Earth and renormalize them to the current best estimate for the mass of the Earth. Using estimates of the uncertainties in i) the density profiles, ii) the core-mantle boundary and iii) the inner core boundary, we employ standard error propagation to obtain a core mass fraction of $32.5 \pm 0.3$ wt%. Our bulk Earth abundances are the weighted sum of our concordance core abundances and concordance PM abundances. Our concordance estimates for the abundances of Mg, Sn, Br, B, Cd and Be are significantly lower than previous estimates of the bulk Earth. Our concordance estimates for the abundances of Na, K, Cl, Zn, Sr, F, Ga, Rb, Nb, Gd, Ta, He, Ar, and Kr are significantly higher. The uncertainties on our elemental abundances usefully calibrate the unresolved discrepancies between standard Earth models under various geochemical and geophysical assumptions.

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