Host: The Japanese Society for Planetary Sciences: Local Organizing Committee for 2006 Fall Meeting
High pressure and high temperature experiments of solid methane were performed in the pressure range of 10 to 81 GPa using diamond-anvil cell and Nd:YAG-laser. Solid methane melted under high temperature and wide pressure range. Three difference regions were distinguished depending on the temperature distribution. In the highest temperature region, difference in refractive index from surrounding solid methane was clearly observed during and after heating. The X-ray diffractmetry and Raman spectroscopy revealed formation of ethane molecules and a van der Waals compound consisting of methane and ethane molecules reported just recently. In the higher temperature region, the crystal structure was solid methane were almost broken but the methane molecules were kept. In the lower temperature region, the samples reverted to the solid methane in spite of melting during heating. According to theoretical studies, the pressure and temperature conditions of the most upper part of middle ice layer of Neptune and Uranus were calculated to be approximately 10GPa and 2000K.On the basis of the experimental results, the upper parts of the middle ice layer might be molten.
