Shocked H 2 O ice: Thermal emission measurements and the criteria for phase changes during impact events

Impact cratering events on icy planetary bodies may produce transient liquid water and vapor. We present the first thermal emission measurements from shocked H 2 O ice and derive peak and post‐shock temperatures. Under shock pressures between 8.2 and 13.6 GPa, initially ∼165 K ice is heated to between 673 and 1055 K. In the time frame of the experiment, the shocked H 2 O releases to the saturation vapor curve and does not achieve full decompression. The temperature results are used to validate the new 5‐Phase H 2 O model equation of state (EOS). The 5‐Phase EOS is used to predict the critical shock pressures required to induce melting and vaporization of ice for a wide range of ambient pressures and temperatures. Impact events with velocities as low as ∼1 km/s will initiate phase changes on icy surfaces. Thus, shock‐induced melting and vaporization of ice is a widespread process in the solar system.