A magma ocean origin to divergent redox evolutions of rocky planetary bodies and early atmospheres
A magma ocean origin to divergent redox evolutions of rocky planetary bodies and early atmospheres
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DOI：
10.1038/s41467-020-15757-0
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发表时间：
2020-04-24
影响因子：
16.6
通讯作者：
Lee, Kanani K. M.
中科院分区：
文献类型：
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作者：
Deng, Jie;Du, Zhixue;Lee, Kanani K. M.
在早期太阳系中，岩浆海洋曾经无处不在，为行星体不同的演化路径提供了初始条件。特别是，岩浆海洋的氧化还原条件可能对后来形成的地幔和上覆大气的氧化还原状态产生深远的影响。然而，相关的氧化还原缓冲反应仍然没有受到很好的限制。使用第一性原理模拟和热力学模型相结合，我们发现地球、火星和月球的岩浆海洋可能具有氧逸度垂直梯度的特征，更深的岩浆海洋需要更多的氧化表面条件。这种氧化还原环带可能是地球上地幔比火星和月球氧化程度更高的主要原因。这些对比鲜明的氧化还原曲线还表明，地球早期的大气主要是二氧化碳和H2O，而火星大气中富含H2O和H-2，月球大气中富含H-2和CO。应用第一性原理分子动力学模拟和热力学模拟，作者提出了地球、火星和月球岩浆海洋中的垂直氧逸度梯度。因此，这项研究提出，与火星或月球等较小的天体相比，地球等较大的行星具有更强的氧化上地幔。
Magma oceans were once ubiquitous in the early solar system, setting up the initial conditions for different evolutionary paths of planetary bodies. In particular, the redox conditions of magma oceans may have profound influence on the redox state of subsequently formed mantles and the overlying atmospheres. The relevant redox buffering reactions, however, remain poorly constrained. Using first-principles simulations combined with thermodynamic modeling, we show that magma oceans of Earth, Mars, and the Moon are likely characterized with a vertical gradient in oxygen fugacity with deeper magma oceans invoking more oxidizing surface conditions. This redox zonation may be the major cause for the Earth's upper mantle being more oxidized than Mars' and the Moon's. These contrasting redox profiles also suggest that Earth's early atmosphere was dominated by CO2 and H2O, in contrast to those enriched in H2O and H-2 for Mars, and H-2 and CO for the Moon. Applying first-principles molecular dynamic simulations and thermodynamic modelling, the authors suggest a vertical oxygen fugacity gradient in magma oceans of Earth, Mars, and the Moon. Consequently, the study proposes larger planets like Earth to have stronger oxidized upper mantles than smaller bodies such as Mars or the Moon.