Shock properties of H₂O ice

Abstract

[1] To understand the mechanics and thermodynamics of impacts on, and collisions between, icy planetary bodies, we measured the dynamic strength and shock states in H 2 O ice. Here, we expand upon previous analyses and present a complete description of the phases, temperature, entropy, and sound velocity along the ice shock Hugoniot. Derived from shock wave measurements centered at initial temperatures (T 0 ) of 100 K and 263 K, the Hugoniot is composed of five regions: (1) elastic shocks in ice Ih, (2) ice Ih deformation shocks, and shock transformation to (3) ice VI, (4) ice VII, and (5) liquid water. In each region, data obtained at different initial temperatures are described by a single U S À Du p shock equation of state. The dynamic strength of ice Ih is strongly dependent on initial temperature, and the Hugoniot Elastic Limit varies from 0.05 to 0.62 GPa, as a function of temperature and peak shock stress. We present new bulk sound velocity measurements and release profiles from shock pressures between 0.4 and 1.2 GPa. We report revised values for the shock pressures required to induce incipient melting (0.6 ± 0.05, 1.6 ± 0.3 GPa) and complete melting (2.5 ± 0.1, 4.1 ± 0.3 GPa) upon isentropic release from the shock state (for T 0 = 263, 100 K). On account of the >40% density increase upon transformation from ice Ih to ices VI and VII, the critical shock pressures required for melting are factors of 2 to 10 lower than earlier predicted. Consequently, hypervelocity impact cratering on planetary surfaces and mutual collisions between porous cometesimals will result in abundant shock-induced melting throughout the solar system.

Glycine oligomerization up to triglycine by shock experiments simulating comet impacts

“…They revealed that the shock temperature of a mixture of water ice and quartz is in good agreement with the Hugoniot temperature of pure water ice. The specific volume at each shock pressure was taken from the Hugoniot data generated by Stewart and Ahrens (2005) and the references provided therein. Because the Hugoniot of ice enters the liquid water fields at 9.2 GPa (Stewart and Ahrens, 2005), we applied the parameter of liquid water from 9.2 GPa.…”

“…The specific volume at each shock pressure was taken from the Hugoniot data generated by Stewart and Ahrens (2005) and the references provided therein. Because the Hugoniot of ice enters the liquid water fields at 9.2 GPa (Stewart and Ahrens, 2005), we applied the parameter of liquid water from 9.2 GPa. The values of C v are 1390 J kg -1 K -1 for ice (Chizhov, 1993) and 3420 J kg -1 K -1 for liquid water (Stewart and Ahrens, 2005).…”

“…Because the Hugoniot of ice enters the liquid water fields at 9.2 GPa (Stewart and Ahrens, 2005), we applied the parameter of liquid water from 9.2 GPa. The values of C v are 1390 J kg -1 K -1 for ice (Chizhov, 1993) and 3420 J kg -1 K -1 for liquid water (Stewart and Ahrens, 2005). The γ values of ice and liquid water were referred to by Leadbetter (1965) and Stewart and Ahrens (2005), respectively.…”

“…The values of C v are 1390 J kg -1 K -1 for ice (Chizhov, 1993) and 3420 J kg -1 K -1 for liquid water (Stewart and Ahrens, 2005). The γ values of ice and liquid water were referred to by Leadbetter (1965) and Stewart and Ahrens (2005), respectively. Hence, in this work, the shock temperatures were calculated to be 450-1170 K (Table 1).…”

“…These calculated temperatures are most likely higher than the real shock temperature because we have not considered the latent heat related to the phase change from ice to liquid. Stewart and Ahrens (2005) reported that the difference between the Hugoniot temperature of liquid water and water ice is not significant and becomes smaller in the high-pressure region (>10 GPa) of the ice Hugoniot. Then, if we recalculate the shock temperatures assuming that the starting material was made of liquid water (298 K) alone, the Hugoniot temperatures are calculated as 460-900 K.…”