Hydrodynamic Instabilities to Measure MgO Viscosity at High Pressures*

Mantle dynamics drive a wide range of processes that shape terrestrial planets such as Earth and super-Earths. Plate tectonics, magnetic field generation, and volcanism are influenced by the mantle's transport properties. However, the viscosity of mantle-building materials, such as MgO, is poorly constrained at relevant pressures. This work focuses on novel experiments to measure the viscosity of MgO under super-Earth mantle conditions, ranging from 50 to 700 GPa. Experiments were conducted at the OMEGA EP laser facility to measure the Richtmyer-Meshkov instability growth at a shocked interface between epoxy and MgO. The growth behavior is strongly influenced by viscosity. We perform simulations using an in-house hydrodynamic code to compare with the experiments, considering MgO viscosities ranging from 0 to 20,000 Pa·s. By comparing these viscous simulations with VISAR data from the experiments, we can provide constraints on MgO viscosity.