Effect of hydrogen on the melting temperature of FeS at high pressure: Implications for the core of Ganymede

Yuki Shibazaki, Eiji Ohtani, Hidenori Terasaki, Ryuji Tateyama, Tatsuya Sakamaki, Taku Tsuchiya, Ken ichi Funakoshi

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28 Citations (Scopus)


We have carried out in situ X-ray diffraction experiments on the FeS-H system up to 16.5GPa and 1723K using a Kawai-type multianvil high-pressure apparatus employing synchrotron X-ray radiation. Hydrogen was supplied to FeS from the thermal decomposition of LiAlH4, and FeSHx was formed at high pressures and temperatures. The melting temperature and phase relationships of FeSHx were determined based on in situ powder X-ray diffraction data. The melting temperature of FeSHx was reduced by 150-250K comparing with that of pure FeS. The hydrogen concentration in FeSHx was determined to be x=0.2-0.4 just before melting occurred between 3.0 and 16.5GPa. It is considered that sulfur is the major light element in the core of Ganymede, one of the Galilean satellites of Jupiter. Although the interior of Ganymede is differentiated today, the silicate rock and the iron alloy mixed with H2O, and the iron alloy could react with H2O (as ice or water) or the hydrous silicate before the differentiation occurred in an early period, resulting in a formation of iron hydride. Therefore, Ganymede's core may be composed of an Fe-S-H system. According to our results, hydrogen dissolved in Ganymede's core lowers the melting temperature of the core composition, and so today, the core could have solid FeSHx inner core and liquid FeHx-FeSHx outer core and the present core temperature is considered to be relatively low.

Original languageEnglish
Pages (from-to)153-158
Number of pages6
JournalEarth and Planetary Science Letters
Issue number1-2
Publication statusPublished - 2011 Jan 3


  • Core
  • Ganymede
  • Hydrogen
  • Iron sulfide
  • Melting temperature
  • Metal hydride


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