Nishida Keisuke, Shibazaki Yuki, Terasaki Hidenori, Higo Yuji, Suzuki Akio, Funamori Nobumasa, Hirose Kei
Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo, 113-0033, Japan.
Bayerisches Geoinstitut, University of Bayreuth, 95440, Bayreuth, Germany.
Nat Commun. 2020 May 13;11(1):1954. doi: 10.1038/s41467-020-15755-2.
Sulfur has been considered to be a predominant light element in the Martian core, and thus the sound velocity of Fe-S alloys at relevant high pressure and temperature is of great importance to interpret its seismological data. Here we measured the compressional sound velocity (V) of liquid Fe, FeS and FeS using ultrasonic pulse-echo overlap method combined with a Kawai-type multi-anvil apparatus up to 20 GPa, likely corresponding to the condition at the uppermost core of Mars. The results demonstrate that the V of liquid iron is least sensitive to its sulfur concentration in the Mars' whole core pressure range. The comparison of seismic wave speeds of Fe-S liquids with future observations will therefore tell whether the Martian core is molten and contains impurity elements other than sulfur.
硫被认为是火星核心中主要的轻元素，因此，铁 - 硫合金在相关高压和温度下的声速对于解释其地震学数据至关重要。在此，我们使用超声脉冲回波重叠法结合川畸型多砧装置，测量了液态铁、FeS和FeS₂在高达20吉帕压力下的纵波声速（V），该压力可能对应火星最上层核心的条件。结果表明，在火星整个核心压力范围内，液态铁的V对其硫浓度最不敏感。因此，将铁 - 硫液体的地震波速度与未来观测结果进行比较，将能够判断火星核心是否处于熔融状态，以及是否含有除硫以外的杂质元素。
