Effects of Hydrogen on the Phase Relations in Fe‐FeS at Pressures of Mars‐Sized Bodies
Effects of Hydrogen on the Phase Relations in Fe‐FeS at Pressures of Mars‐Sized Bodies
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DOI：
10.1029/2021je006942
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发表时间：
2021-05
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影响因子：
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通讯作者：
H. Piet;K. Leinenweber;E. Greenberg;V. Prakapenka;S. Shim
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作者：
H. Piet;K. Leinenweber;E. Greenberg;V. Prakapenka;S. Shim
在InSight使命数据分析中发现的火星核心的大半径，因此低密度，突出了考虑除硫（S）之外的其他轻元素的重要性，硫（S）几十年来一直被认为是火星的主要轻元素。氢（H）在太阳系中含量丰富，在高压下成为亲铁体。尽管Fe-S和Fe-H体系已被单独研究，但Fe-S-H三元体系仅在高达16 GPa和1723 K的压力下进行了研究。我们研究了Fe-S-H系统在与火星大小的行星核心相关的压力和温度（P-T）（高达45 GPa，远高于FeS的熔化温度）下，在激光加热金刚石对顶砧单元中结合原位同步X射线衍射。我们发现，足够的氢导致Fe 3S在高P-T下消失。相反，单独的Fe-H和Fe-S相出现在23-35 GPa。在35 GPa以上的压力下，我们发现一个新的相出现，而Fe-S相消失，Fe-H相保留。我们的分析表明，新相的晶体结构中可能含有S和H（暂定为FeSxHy，其中x ≤ 1，y ≤ 1）。所观察到的相位关系中的压力依赖性变化可能对于理解火星核心和火星大小的系外行星核心的结构和动力学非常重要。
The large radius, and therefore low density, of the Martian core found in the InSight mission data analysis highlights the importance of considering other light elements besides sulfur (S), which has been considered as the main light element for Mars for decades. Hydrogen (H) is abundant in the solar system and becomes siderophile at high pressures. Although Fe‐S and Fe‐H systems have been studied individually, the Fe‐S‐H ternary system has only been investigated up to 16 GPa and 1723 K. We have investigated the Fe‐S‐H system at pressures and temperatures (P‐T) relevant to the cores of Mars‐sized planets (up to 45 GPa and well above the melting temperature of FeS) in the laser‐heated diamond anvil cell combined with in situ synchrotron X‐ray diffraction. We found that sufficient hydrogen leads to the disappearance of Fe3S at high P‐T. Instead, separate Fe‐H and Fe‐S phases appear at 23–35 GPa. At pressures above 35 GPa, we found a new phase appearing while Fe‐S phases disappear and Fe‐H phases remain. Our analysis indicates that the new phase likely contains both S and H in the crystal structure (tentatively FeSxHy where x ≈ 1 and y ≈ 1). The observed pressure‐dependent changes in the phase relation may be important for understanding the structure and dynamics of the Martian core and the cores of Mars‐sized exoplanets.