1. National Institute of Polar Research (NIPR) 10‐3 Midori‐cho Tachikawa Tokyo 190‐8518 Japan
2. Department of Basic Science The University of Tokyo 3‐8‐1 Komaba Meguro‐ku Tokyo 153‐8902 Japan
3. The University Museum The University of Tokyo 7‐3‐1 Hongo Bunkyo‐ku Tokyo 113‐0033 Japan
4. National Institute for Materials Science (NIMS) 1‐1 Namiki Tsukuba Ibaraki 305‐0044 Japan
5. Center for High Pressure Science and Technology Advanced Research (HPSTAR) 1690 Cailun Rd Pudong Shanghai 201203 P.R. China
6. Graduate School of Engineering Osaka University 2‐1 Yamadaoka Suita Osaka 565‐0871 Japan
7. Department of Polar Science School of Multidisciplinary Science SOKENDAI (The Graduate University for Advanced Studies) Tachikawa Tokyo 190‐8518 Japan
8. Department of Earth and Planetary Science The University of Tokyo 7‐3‐1 Hongo Bunkyo‐ku Tokyo 113‐0033 Japan