Kinetics of compaction of granular ices H2O, CO2 and (NH3)x(H2O)1 −x at pressures of 2–20 MPa and in temperatures of 100–270 K. Application to the physics of the icy satellites

Experimental studies of compaction of ices are dealt with. They are in the form of granular, then initially porous samples. The ices are: H2O, CO2, and (NH3)x(H2O)1−x. A piston-cylinder device is used. The initial volume of the samples is around 50 cm3. Their initial porosity (prior to compaction) is between 0.2 and 0.4. The duration of one run is 10–15 h. The pressures applied in the experiments are 3.7, 6.55, and 13.1 MPa. Temperature ranges from that of a liquid nitrogen cooling medium (78 K) up to about 270 K for H2O ice, about 195 K for CO2 ice, and about 150 K for water/ammonia ices. A formula for the rate of decrease of porosity q ˙ = − q f ( q , p , T ) exp (−Q/RT) is fitted to the experimental data. It is found that Q = 25 kJ mol−1 for CO2 ice and Q = (39−105x) kJ mol−1 for water/ammonia ices with 0 ⩽ x ⩽ 0.28. The consequences of the kinetics of densification of different ices on the growth of the icy satellite Mimas are discussed.