Tagawa Shoh, Sakamoto Naoya, Hirose Kei, Yokoo Shunpei, Hernlund John, Ohishi Yasuo, Yurimoto Hisayoshi
Department of Earth and Planetary Science, The University of Tokyo, Bunkyo, Tokyo, 113-0033, Japan.
Creative Research Institution (CRIS), Hokkaido University, Sapporo, Hokkaido, 001-0021, Japan.
Nat Commun. 2021 May 11;12(1):2588. doi: 10.1038/s41467-021-22035-0.
Hydrogen is one of the possible alloying elements in the Earth's core, but its siderophile (iron-loving) nature is debated. Here we experimentally examined the partitioning of hydrogen between molten iron and silicate melt at 30-60 gigapascals and 3100-4600 kelvin. We find that hydrogen has a metal/silicate partition coefficient D ≥ 29 and is therefore strongly siderophile at conditions of core formation. Unless water was delivered only in the final stage of accretion, core formation scenarios suggest that 0.3-0.6 wt% H was incorporated into the core, leaving a relatively small residual HO concentration in silicates. This amount of H explains 30-60% of the density deficit and sound velocity excess of the outer core relative to pure iron. Our results also suggest that hydrogen may be an important constituent in the metallic cores of any terrestrial planet or moon having a mass in excess of ~10% of the Earth.
氢是地核中可能存在的合金元素之一，但其亲铁性（爱铁性）仍存在争议。在此，我们通过实验研究了在30 - 60吉帕斯卡压力和3100 - 4600开尔文温度下，氢在铁熔体和硅酸盐熔体之间的分配情况。我们发现，氢的金属/硅酸盐分配系数D≥29，因此在核形成条件下具有很强的亲铁性。除非水仅在吸积的最后阶段才被输送，否则核形成模型表明，有0.3 - 0.6 wt%的氢被纳入地核，从而在硅酸盐中留下相对较低的残余氢氧浓度。这一数量的氢解释了外核相对于纯铁的30 - 60%的密度亏损和声速过剩。我们的研究结果还表明，对于任何质量超过地球质量约10%的类地行星或卫星，氢可能是其金属核中的一种重要成分。
