High Pressure Viscosity Measurements of Planetary Fluids

We have measured the viscosity of argon to 1.5 GPa and 353 Kelvin, 4% sodium-chloride water solution to 1.1 GPa at room temperature, and water up to 4.0 GPa and 500 Kelvin using an externally-heated, rolling-sphere diamond-cell viscometer. The viscosity of argon increases by a factor of three between 0.5 GPa and the crystallization pressure of 1.2 GPa. The viscosity of the sodium-chloride solution exhibits the same relative change as pure water, about a factor of 2 over 1 GPa. Surprisingly, we were able to compress water past the crystallization pressure at room temperature, and measure viscosity of metastable liquid water up to 1.4 GPa. The maximum viscosity attained was ~ 3 mPa*s, and appears to be consistent with simple extrapolations from both the low-pressure data (< 1 GPa) and the high-temperature, high-pressure data (> 323 K, ~1.5 GPa). Virtually no data previously existed for aqueous solutions at high pressures, and our experiments increase the pressure range for extensive viscosity measurements on H2O and Ar by 50%. Measurements using the diamond-cell viscometer with heating capability provide significant tests of theoretical models of fluid-transport properties at conditions existing deep inside planets.