COMPOSITIONAL EVOLUTION DURING ROCKY PROTOPLANET ACCRETION
COMPOSITIONAL EVOLUTION DURING ROCKY PROTOPLANET ACCRETION
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DOI：
10.1088/0004-637x/813/1/72
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发表时间：
2015-11-01
影响因子：
4.9
通讯作者：
Stewart, Sarah T.
中科院分区：
文献类型：
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作者：
Carter, Philip. J.;Leinhardt, Zoe M.;Stewart, Sarah T.
地球在难熔亲石元素的丰度上呈现出非球粒陨石特征，这对我们理解地球的形成和演化构成了重大问题。有人提出，这种非球粒陨石成分可能是由原本具有球粒陨石成分的分化小行星的碰撞侵蚀所导致的。在这项工作中，我们展示了类地行星形成的N体模拟，该模拟追踪小行星体形成行星胚胎的过程。我们在大转向模型下以及在没有巨行星的情况下模拟了失控生长和寡头生长阶段的演化。这些模拟包括一个最先进的碰撞模型，该模型允许多种碰撞结果，例如吸积、侵蚀和反弹事件，并能够追踪吸积小行星体不断变化的核质量分数。我们表明，在行星形成的这个中间阶段生长的胚胎呈现出一系列的核质量分数，并且在显著的动力学激发下，足够的地幔可以从生长的胚胎中被剥离，以解释地球的非球粒陨石铁/镁比。我们还发现，残余小行星体的成分存在很大差异，通过碰撞产生了富铁和富硅酸盐的碎片。
The Earth appears non-chondritic in its abundances of refractory lithophile elements, posing a significant problem for our understanding of its formation and evolution. It has been suggested that this non-chondritic composition may be explained by collisional erosion of differentiated planetesimals of originally chondritic composition. In this work, we present N-body simulations of terrestrial planet formation that track the growth of planetary embryos from planetesimals. We simulate evolution through the runaway and oligarchic growth phases under the Grand Tack model and in the absence of giant planets. These simulations include a state-of-the-art collision model that allows multiple collision outcomes, such as accretion, erosion, and bouncing events, and enables tracking of the evolving core mass fraction of accreting planetesimals. We show that the embryos grown during this intermediate stage of planet formation exhibit a range of core mass fractions, and that with significant dynamical excitation, enough mantle can be stripped from growing embryos to account for the Earth's non-chondritic Fe/Mg ratio. We also find that there is a large diversity in the composition of remnant planetesimals, with both iron-rich and silicate-rich fragments produced via collisions.