The shock Hugoniot of Fe-free and Fe-bearing enstatite to 1.7 TPa

Polymorphs of MgSiO₃ are the most abundant minerals in the Earth and are common components of other terrestrial planets. How these minerals behave under extreme conditions can inform us of the processes of planet formation and the dynamics of planetary interiors. Here, we extend the shock Hugoniot of Fe-free enstatite to 1700 GPa and we present the first shock compression and shock temperature data of Fe-bearing enstatite ((Mg_0.9,Fe_0.1)SiO₃, bronzite) between 200 and 1600 GPa. We find that adding Fe to the enstatite system makes the silicate liquids more compressible at relatively low-pressures, but that these fluids stiffen rapidly at higher pressures. Somewhat surprisingly, despite the differences in compressibility, the shock temperatures for Fe-free and Fe-bearing enstatite are identical within error, suggesting some compensating effects in the heat capacity of these materials. These data will be used to inform models of giant impacts for planets with more realistic chemical compositions.