Knowledge of the elasticity of high‐pressure ice is key to constructing the internal structure of various planetary bodies. Here, we present direct experimental constraints on the single‐crystal elasticity of ice with 0.5 mol/L (0.9 mol.%) NaCl up to 98 GPa at 300 K. The change from ice‐VII to the dynamically disordered ice‐VII is characterized by an obvious softening of the longitudinal and bulk moduli between 42.4 and 46 GPa. Further transition to ice X at ∼64 GPa results in an apparent change in the pressure dependence for the elasticity. Using the obtained elasticity, our modelling reveals that the boundary between the ice‐VII layer and the silicate mantle or core in moderate‐size icy planetary bodies would be associated with a sudden velocity jump. In large planetary bodies, the change from ice X to the silicate layer will be characterized by an abrupt reduction in velocity.

Shi, W.Sun, N.Li, X.Mao, Z.Liu, J., & Prakapenka, V. B. (2021). Singlecrystal elasticity of highpressure ice up to 98 GPa by brillouin scatteringGeophysical Research Letters48, e2021GL092514. abstract