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: H2 O, CO2, and (NH3)(x)(H2O)(1-x). A piston-cylinder device is used. The initial volume of the samples is around 50 cm(3). Their initial porosi ty (prior to compaction) is between 0.2 and 0.4. The duration of one r un 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 cooli ng medium (78 K) up to about 270 K for H2O ice, about 195 K for CO2 ic e, and about 150 K for water/ammonia ices. A formula for the rate of d ecrease of porosity q = -qf(q, p, T) exp (-Q/RT) is fitted to the expe rimental 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 less than or equal t o x less than or equal to 0.28. The consequences of the kinetics of de nsification of different ices on the growth of the icy satellite Mimas are discussed.