The 9th International Conference on Matter and Radiation at Extremes (ICMRE2026) ( ICMRE2026)

Constraining the equation of state (EOS) and phase behavior of planetary minerals is essential for understanding the evolution of Super-Earths. Magnesium silicate, a dominant mantle constituent, has long exhibited uncertain structural responses under the extreme pressures and temperatures of such massive rocky planets. Here, we report high-precision shock Hugoniot measurements of MgSiO₃ enstatite up to 330 GPa and 8200 K using a three-stage gas gun. Combined with the calculated Hugoniot curves and phase diagrams via ab-initio machine learning simulations, our results reveal that shock compression drives enstatite into post-perovskite phase. Moreover, a pronounced temperature plateau along Hugoniot between 175 and 203 GPa provides clear evidence for melting, leading to a revised melting curve of MgSiO₃. The relatively slow temperature increasing in the melting curve implies that silicate melts could persist at extreme depths, promoting the formation of a basal magma ocean in massive super-Earths.
 

Shock compression, enstatite, machine-learning potential, structural evolution, melting