[S-IT25] Planetary cores: Structure, formation, and evolution

[SIT25-03] P-wave velocity of Fe₃S under high pressure and temperature

*鎌田 誠司^1,2、寺崎 英紀³、福井 宏之^4,5、坂巻 竜也²、内山 裕士⁶、筒井 智嗣⁶、大谷 栄治²、Baron Alfred⁵ (1.東北大学学際科学フロンティア研究所、2.東北大学大学院理学研究科地学専攻、3.大阪大学大学院理学研究科宇宙地球科学専攻、4.兵庫県立大学物質理学研究科物質科学専攻、5.RIKEN、6.JASRI)

キーワード：非弾性X線散乱法、ダイヤモンドアンビルセル、レーザー加熱

Martian cores have been thought to include a certain amount of sulfur as a light element. Sohl and Spohn (1997) proposed seismic wave velocity and density profiles of the interior of Mars based on equations of state of core matrials although seismic wave velocities of core materials are needed for presice estimation. However, there have been only a limited number of works for V_P of Fe alloys with sulfur. In the Fe-FeS system, V_P of FeS and FeS₂ have been studied (e.g. Badro et al. 2007) but these compounds are not appropriate for the core materials of Mars because Fe₃S is a stable phase above 20 GPa corresponding to Martian core conditions (Fei et al., 1997, 2000) up to at least 200 GPa (Kamada et al., 2010, 2012). Therefore, Fe₃S is a subsolidus phase together with ε-Fe in the Fe-Fe₃S system at Martian core conditions and it is essential to study V_P of Fe₃S to understand seismic properties of the Martian core. We have measured sound V_P of Fe₃S under high temperature and pressure at BL35XU of SPring-8.
In this study, a synthesized Fe₃S was used as a starting material. A symmetric diamond anvil cell was used to generate high pressures. IXS(Inelastic X-ray Scattering) and XRD experiments were performed at the beamline 35XU of SPring-8, Japan (Baron et al., 2000). V_P of Fe₃S were measured up to 100 GPa and 2000 K. We will discuss temperature effect on the V_P of Fe₃S and the Birch's law and seismic wave velocity profile of the Martian core.