Loss and Fractionation of Noble Gas Isotopes and Moderately Volatile Elements from Planetary Embryos and Early Venus, Earth and Mars
Loss and Fractionation of Noble Gas Isotopes and Moderately Volatile Elements from Planetary Embryos and Early Venus, Earth and Mars
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DOI：
10.1007/s11214-020-00701-x
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发表时间：
2020-06
影响因子：
10.3
通讯作者：
H. Lammer;M. Scherf;H. Kurokawa;Y. Ueno;C. Burger;T. Maindl;C. Johnstone;Martin Leizinger;Markus Benedikt;L. Fossati;K. Kislyakova;B. Marty;G. Avice;B. Fegley;P. Odert
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文献类型：
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作者：
H. Lammer;M. Scherf;H. Kurokawa;Y. Ueno;C. Burger;T. Maindl;C. Johnstone;Martin Leizinger;Markus Benedikt;L. Fossati;K. Kislyakova;B. Marty;G. Avice;B. Fegley;P. Odert
在这里，我们讨论目前关于大气逃逸过程如何分馏存在于原始大气、岩浆海洋相关环境和灾难性脱气蒸汽大气中的稀有气体同位素和中等挥发性造岩元素的知识。不同行星库中同位素和挥发性元素的变化保存了有关大气逃逸、成分甚至吸积物质来源的信息。我们总结了关于大气同位素比的知识，并讨论了原金星和地球捕获了以氢为主的小型原始大气的最新证据，这些大气在圆盘分散期间和之后因流体动力逃逸而消失。讨论了可以分馏各种同位素和挥发性元素的所有相关热和非热大气逃逸过程。还讨论了大型行星撞击体对早期大气、地壳和地幔的侵蚀。此外，我们还讨论了中等挥发性元素（例如放射性产热元素40K）和其他岩石形成元素（例如Na）如何从源自大型行星胚胎和吸积行星的岩浆海洋中释放和损失。脱气元素从行星胚胎中逸出，其质量是直接逸出的，或者是由于逸出的氢原子的流体动力阻力而逸出的，氢原子源自质量更大的胚胎的原始大气或蒸汽大气。我们讨论这些过程如何影响最终的元素组成和比率，例如早期行星及其构建块的 K/U、Fe/Mg。最后，我们回顾了通过再现目前测量的大气 36Ar/38Ar、20Ne/22Ne、稀有气体同位素比率以及同位素对水损失的作用及其与早期火星氧化还原状态的联系来限制金星、地球和火星早期演化的建模工作。
Here we discuss the current state of knowledge on how atmospheric escape processes can fractionate noble gas isotopes and moderately volatile rock-forming elements that populate primordial atmospheres, magma ocean related environments, and catastrophically outgassed steam atmospheres. Variations of isotopes and volatile elements in different planetary reservoirs keep information about atmospheric escape, composition and even the source of accreting material. We summarize our knowledge on atmospheric isotope ratios and discuss the latest evidence that proto-Venus and Earth captured small H2-dominated primordial atmospheres that were lost by hydrodynamic escape during and after the disk dispersed. All relevant thermal and non-thermal atmospheric escape processes that can fractionate various isotopes and volatile elements are discussed. Erosion of early atmospheres, crust and mantle by large planetary impactors are also addressed. Further, we discuss how moderately volatile elements such as the radioactive heat producing element40K and other rock-forming elements such as Na can also be outgassed and lost from magma oceans that originate on large planetary embryos and accreting planets. Outgassed elements escape from planetary embryos with masses that aredirectly, or due to hydrodynamic drag of escaping H atoms originating from primordial- or steam atmospheres at more massive embryos. We discuss how these processes affect the final elemental composition and ratios such as K/U, Fe/Mg of early planets and their building blocks. Finally, we review modeling efforts that constrain the early evolution of Venus, Earth and Mars by reproducing their measured present day atmospheric36Ar/38Ar,20Ne/22Ne, noble gas isotope ratios and the role of isotopes on the loss of water and its connection to the redox state on early Mars.