Japan Geoscience Union Meeting 2019

Presentation information

[E] Oral

P (Space and Planetary Sciences ) » P-CG Complex & General

[P-CG22] Shock responses of planetary materials elucidated from meteorites and dynamic compression experiments

Tue. May 28, 2019 3:30 PM - 5:00 PM A03 (TOKYO BAY MAKUHARI HALL)

convener:Toshimori Sekine(Center for High Pressure Science and Technology Advanced Research), Takuo Okuchi(Institute for Planetary Materials, Okayama University), Chairperson:Takuo Okuchi(Okayama University), Yongjae Lee(Yonsei University)

4:00 PM - 4:15 PM

[PCG22-09] Hugoniot measurements for silicate: Understanding silicate magma under the planetary impacts

*Yuhei Umeda1, Norimasa Ozaki1, Toshimori Sekine2, Bruno Albertazzi3, Alessandra Benuzzi-Mounaix3, Riccardo Bolis3, Marco Guaruaglini3, Kento Katagiri1, Kodama Ryosuke1, Michel Koeing3, Kohei Miyanishi4, Shintaro Morioka1, Toyohito Nishikawa1, Syugo Ohi5, Alessandra Ravasio3, Yoichi Sakawa4, Takayoshi Sano4, Tomoko Sato6 (1.Graduate School of Engineering, Osaka Univ., 2.Center for High Pressure Science & Technology Advanced Research, 3.Ecole Polytechnique, 4.Institute of Laser Engineering, Osaka University, 5.Shiga Univ., 6.Graduate School of Science, Hiroshima University)

Two magnesium silicates of MgSiO3(Enstatite) and Mg2SiO4(Forsterite) are primary mantle constitutions in the Earth and major components in Earth-type exoplanets.The ordinary chondrite, which accounts for about 90 % of all flying meteorites, consists of silicates as main components. The impacts at collision velocities exceeding 10 km/s are known as common events in the universe and such high energy phenomena could have played an important role to form planets or planetesimals and to evolve planetary environments. For example, a large-scale impact such as the giant impact related to the formation of moon was estimated to be at impact velocity of 15-20 km/s [Melosh, 1990].

In this study, Hugoniot equation of state (EOS) of enstatite has been determined at pressures of ~400 to 560 GPa by laser shock experiments. A coupling of both the present study and the previous data by Fratanduono et al. (2018) shows a discontinuity in the shock velocity-particle velocity at ~380-400 GPa. The measured reflectivity of shocked enstatite indicates three different trends relative to that of quartz; less steep slope at 300-345 GPa, parallel at 345-400 GPa, and a rapid increasing above ~400 GPa, suggesting different phases of enstatite melt, a mixture of metal-like liquid of SiO2and crystalline MgO, and fluid-like enstatite melt above ~380 GPa. We also calculated the release state of thin enstatite using quartz on it as a reference. These results on enstatite imply that reactions in silicate magma occur at pressures of 300-400 GPa and that they may affect the current planet formation model in terms of the stratification of interior, the mantle convection, and the formation of magnetic field in Super-Earths.