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arXiv 1209.3635astro-ph.EP
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关于类地行星元素丰度的起源

On the origin of elemental abundances in the terrestrial planets

Sebastian Elser, Michael R. Meyer, Ben Moore

摘要:

地球和类地行星中丰富的元素为生命提供了初始条件,也为太阳系的历史和形成提供了线索。我们遵循Bond et al.(2010)的开创性工作,结合拱星盘模型、化学平衡计算和行星形成的动力学模拟来研究岩石行星的整体组成。我们使用凝聚序列计算来估计初始丰度的固体在拱盘与时间相关的理论模型确定的属性。我们结合动力学模拟的星子生长,跟踪固体在行星形成过程中。我们计算了由此产生的行星中的元素丰度,并探讨了这些元素丰度如何随磁盘模型的选择和太阳星云内的初始条件而变化。虽然太阳系中类地行星的某些特征可以重现,但我们的模型都无法重现所有行星的丰度特性。我们发现,初始的星子盘质量和磁盘模型的选择有一个显着的组成梯度的影响。由于元素丰度分布的不均匀性和动力学模拟中行星的不同源区,给出更高压力和温度的盘模型导致所产生行星的大量化学成分变化更大。我们观察到一种趋势,即大质量行星和半长轴相对较小的行星比径向距离较大的小行星对这些变化更敏感。只有这些大的变化,在模拟的化学丰度可能解释不同的散装组成的太阳系行星,而水星的散装组成不能在我们的方法中重现。

英文摘要:

The abundances of elements in the Earth and the terrestrial planets provide the initial conditions for life and clues as to the history and formation of the Solar System. We follow the pioneering work of Bond et al. (2010) and combine circumstellar disk models, chemical equilibrium calculations and dynamical simulations of planet formation to study the bulk composition of rocky planets. We use condensation sequence calculations to estimate the initial abundance of solids in the circumstellar disk with properties determined from time dependent theoretical models. We combine this with dynamical simulations of planetesimal growth that trace the solids during the planet formation process. We calculate the elemental abundances in the resulting planets and explore how these vary with the choice of disk model and the initial conditions within the Solar Nebula. Although certain characteristics of the terrestrial planets in the Solar System could be reproduced, none of our models could reproduce the abundance properties of all the planets. We found that the choice of the initial planetesimal disk mass and of the disk model has a significant effect on composition gradients. Disk models that give higher pressure and temperature result in larger variations in the bulk chemical compositions of the resulting planets due to inhomogeneities in the element abundance profiles and due to the different source regions of the planets in the dynamical simulations. We observed a trend that massive planets and planets with relatively small semi-major axes are more sensitive to these variations than smaller planets at larger radial distance. Only these large variations in the simulated chemical abundances can potentially explain the diverse bulk composition of the Solar System planets, whereas Mercury's bulk composition can not be reproduced in our approach.

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