Primitive meteorites preserve the chemical and isotopic composition of the first aggregates that formed from dust and gas in the solar nebula during the earliest stages of solar system evolution. Gradual increase in the size of solid bodies from dust to aggregates and then to planetesimals finally led to the formation of planets within a few to tens of million years after the start of condensation. Thus the rocky planets of the inner solar system are likely the result of the accumulation of numerous smaller primitive as well as differentiated bodies. The chemically most primitive known meteorites are chondrites and they consist mostly of metal and silicates. Chondritic meteorites are derived from distinct primitive planetary bodies that experienced only limited element fractionation during formation and subsequent differentiation. Different chondrite classes show distinct chemical and isotopic characteristics, which may reflect heterogeneities in the solar nebula and the slightly different pathways of their formation. To a first approximation the chemical composition of the bulk Earth bears great similarities to primitive meteorites. However, for some elements there are striking and significant differences. The Earth shows a much stronger depletion of the moderate to highly volatile elements compared to chondrites. In addition, mixing trends of specific isotopes reveal that the Earth is most enriched in s $s$ -process isotopes compared to all other analysed bulk solar system materials. It is currently not possible to fully define and quantify the different chemical and isotopic materials that formed the Earth, because a major component seems missing in the extant collections of extraterrestrial samples. Variations in nucleosynthetic isotope compositions as well as the strong depletion of moderately and strongly volatile elements points towards a source in the inner solar system for this missing material. It is conceivable that Venus and Mercury contain a much larger fraction of this missing component. Thus, for a complete reconstruction of the conditions that led to the formation of the inner solar system planets (Mercury to Mars) samples from the inner planets Venus and Mercury are of great interest and importance. High precision chemical and isotopic analyses in the laboratory of rocky material from inner solar system bodies could complete the knowledge on the chemical, isotopic and mineralogical make-up of the solar nebula just prior to planet formation and enhance our understanding of the evolution of the solar nebula in general and the formation of the rocky planets in particular.

中文翻译：

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地球的吸积——缺失的成分？

原始陨石保留了太阳系演化最早阶段由太阳星云中的尘埃和气体形成的第一批聚集体的化学和同位素组成。从尘埃到聚集体，再到星子，固体的大小逐渐增加，最终导致在凝结开始后的几万到几千万年内形成行星。因此，太阳系内部的岩石行星很可能是许多较小的原始和分化天体堆积的结果。化学上最原始的已知陨石是球粒陨石，它们主要由金属和硅酸盐组成。球粒陨石来自不同的原始行星体，这些行星体在形成和随后的分化过程中仅经历了有限的元素分馏。不同的球粒陨石类别显示出不同的化学和同位素特征，这可能反映了太阳星云的异质性及其形成途径略有不同。大体地球的化学成分与原始陨石有很大的相似之处。但是，对于某些元素，存在显着且显着的差异。与球粒陨石相比，地球显示出更强烈的中度至高度挥发性元素的消耗。此外，特定同位素的混合趋势表明，与所有其他分析的大块太阳系材料相比，地球在 s$s$ 过程同位素中含量最高。目前无法完全定义和量化形成地球的不同化学和同位素材料，因为在现存的外星样本集合中似乎缺少一个主要成分。核合成同位素组成的变化以及中度和强挥发性元素的强烈消耗表明，这种缺失材料在太阳系内部有一个来源。可以想象，金星和水星包含这一缺失成分的大部分。因此，对于导致内太阳系行星（水星到火星）形成的条件的完整重建，来自内行星金星和水星的样本具有极大的兴趣和重要性。对太阳系内部天体的岩石物质进行实验室的高精度化学和同位素分析，可以完成对化学、