The processes of planet formation in our Solar System resulted in a final product of a small number of discreet planets and planetesimals characterized by clear compositional distinctions. A key advance on this subject was provided when nucleosynthetic isotopic variability was discovered between different meteorite groups and the terrestrial planets. This information has now been coupled with theoretical models of planetesimal growth and giant planet migration to better understand the nature of the materials accumulated into the terrestrial planets. First order conclusions include that carbonaceous chondrites appear to contribute a much smaller mass fraction to the terrestrial planets than previously suspected, that gas-driven giant planet migration could have pushed volatile-rich material into the inner Solar System, and that planetesimal formation was occurring on a sufficiently rapid time scale that global melting of asteroid-sized objects was instigated by radioactive decay of 26Al. The isotopic evidence highlights the important role of enstatite chondrites, or something with their mix of nucleosynthetic components, as feedstock for the terrestrial planets. A common degree of depletion of moderately volatile elements in the terrestrial planets points to a mechanism that can effectively separate volatile and refractory elements over a spatial scale the size of the whole inner Solar System. The large variability in iron to silicon ratios between both different meteorite groups and between the terrestrial planets suggests that mechanisms that can segregate iron metal from silicate should be given greater importance in future investigations. Such processes likely include both density separation of small grains in the nebula, but also preferential impact erosion of either the mantle or core from differentiated planets/planetesimals. The latter highlights the important role for giant impacts and collisional erosion during the late stages of planet formation.

中文翻译：

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类地行星的原料

我们太阳系中行星形成的过程导致了少数谨慎的行星和微星的最终产物，这些行星和星子的特征是明显的成分差异。当在不同陨石群和类地行星之间发现核合成同位素变异性时，该主题取得了重大进展。这些信息现在已与微行星生长和巨行星迁移的理论模型相结合，以更好地了解积累到类地行星中的物质的性质。一级结论包括碳质球粒陨石对类地行星的贡献似乎比以前怀疑的要小得多，气体驱动的巨行星迁移可能将富含挥发性物质推入太阳系内部，并且小行星的形成发生在足够快的时间尺度上，以至于小行星大小的物体的全球熔化是由 26Al 的放射性衰变引起的。同位素证据突显了顽火球粒陨石或含有核合成成分的混合物作为类地行星原料的重要作用。类地行星中中等挥发性元素的普遍消耗程度表明，一种机制可以在整个内太阳系大小的空间尺度上有效地分离挥发性元素和难熔元素。不同陨石群之间和类地行星之间铁硅比的巨大差异表明，在未来的研究中，应该更加重视将铁金属与硅酸盐分离的机制。这些过程可能包括星云中小颗粒的密度分离，以及来自分化行星/微行星的地幔或地核的优先撞击侵蚀。后者强调了行星形成后期巨大撞击和碰撞侵蚀的重要作用。