Effect of sulfur on sound velocity of liquid iron under Martian core conditions

Keisuke Nishida; Yuki Shibazaki; Hidenori Terasaki; Yuji Higo; Akio Suzuki; Nobumasa Funamori; Kei Hirose

doi:10.1038/s41467-020-15755-2

Effect of sulfur on sound velocity of liquid iron under Martian core conditions

Nat Commun. 2020 May 13;11(1):1954. doi: 10.1038/s41467-020-15755-2.

Authors

Keisuke Nishida^{1

2}, Yuki Shibazaki^{3

4}, Hidenori Terasaki⁵, Yuji Higo⁶, Akio Suzuki⁷, Nobumasa Funamori⁸, Kei Hirose^{9

10}

Affiliations

¹ Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo, 113-0033, Japan. Keisuke.Nishida@uni-bayreuth.de.
² Bayerisches Geoinstitut, University of Bayreuth, 95440, Bayreuth, Germany. Keisuke.Nishida@uni-bayreuth.de.
³ Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, 6-3 Aoba, Aramaki, Aoba, Sendai, 980-8578, Japan.
⁴ International Center for Young Scientists, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan.
⁵ Department of Earth and Space Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka, 560-0043, Japan.
⁶ Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo-cho, Sayo, Hyogo, 679-5198, Japan.
⁷ Department of Earth Science, Tohoku University, 6-3 Aoba, Aramaki, Aoba, Sendai, 980-8578, Japan.
⁸ Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki, 305-0801, Japan.
⁹ Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo, 113-0033, Japan.
¹⁰ Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo, 152-8550, Japan.

Abstract

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_P) of liquid Fe, Fe₈₀S₂₀ and Fe₅₇S₄₃ 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_P 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.

Abstract

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