A wet heterogeneous mantle creates a habitable world in the Hadean
A wet heterogeneous mantle creates a habitable world in the Hadean
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DOI：
10.1038/s41586-021-04371-9
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发表时间：
2022-03
期刊：
影响因子：
64.8
通讯作者：
Y. Miyazaki;J. Korenaga
中科院分区：
文献类型：
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作者：
Y. Miyazaki;J. Korenaga
在全球范围的地幔融化之后的冥古宙，被认为是一个动态时期，在此期间，地球经历了截然不同的状况。然而，地质记录表明，到冥古宙中期，地球的表面环境已经与现在相似。恶劣的地表环境在什么条件下可以变成宜居环境仍然不确定。在这里，我们展示了岩浆海洋凝固产生的具有小规模化学异质性的水合地幔，是海洋形成的关键，板块构造的开始和温室气体的快速清除，这些都是在类地行星上创造宜居环境所必需的。当地幔潮湿且以高镁辉石岩为主时，从大气中去除二氧化碳的速度预计将比辉石岩均质地幔的情况快10倍以上，并可在1.6亿年内完成。这种化学不均匀的地幔也会产生富含橄榄石的海洋地壳，橄榄石与海水反应，促进蛇纹岩化。因此，类似失落之城热液场的条件可能在冥古宙海底全球存在。
The Hadean eon, following the global-scale melting of the mantle, –, is expected to be a dynamic period, during which Earth experienced vastly different conditions. Geologic records, however, suggest that the surface environment of Earth was already similar to the present by the middle of the Hadean,. Under what conditions a harsh surface environment could turn into a habitable one remains uncertain. Here we show that a hydrated mantle with small-scale chemical heterogeneity, created as a result of magma ocean solidification, is the key to ocean formation, the onset of plate tectonics and the rapid removal of greenhouse gases, which are all essential to create a habitable environment on terrestrial planets. When the mantle is wet and dominated by high-magnesium pyroxenites, the removal of carbon dioxide from the atmosphere is expected to be more than ten times faster than the case of a pyrolitic homogeneous mantle and could be completed within 160 million years. Such a chemically heterogeneous mantle would also produce oceanic crust rich in olivine, which is reactive with ocean water and promotes serpentinization. Therefore, conditions similar to the Lost City hydrothermal field, –may have existed globally in the Hadean seafloor.