KINETICS OF PRESSURE-INDUCED EFFECTS IN WATER ICE ROCK GRANULAR MIXTURES AND APPLICATION TO THE PHYSICS OF THE ICY SATELLITES

This paper concerns the rheological experiments on compaction of water and ice and water ice/rock samples prepared from granular material. T he rock to total mass ratio was C = 0, 0.25, 0.465, 0.5, 1 for five di fferent samples. The temperature was kept constant, T = 213 K, for all experimental runs. The pressure regime, p = 80-820 MPa, is that which is interesting from the point of view of the physics and evolution of the interiors of the icy satellites of the giant planets. The densifi cation rate, (drho/dt)/rho, encountered in the experiments decreased f rom some 10(-4) s-1 at the beginning of a run to (10(-7)-10(-8)) s-1 a t the end, some hours later. The densification rate itself mainly repr esents: (i) the rate of decrease of porosity (dq/dt)/q, when the press ure is relatively low (lower than the phase transition pressure ice I double-line arrow pointing right ice II, approximately 200 MPa), and ( ii) the kinetics of the phase transitions ice I double-line arrow poin ting right ice II double-line arrow pointing right ice VI when the pre ssure exceeds 200 and 600 MPa, respectively. The appropriate formulae were fitted to the experimental data: (i) the formula for the rate of decrease of porosity; it is of the same type as it was established pre viously for pressure up to 17.7 MPa (Leliwa-Kopystynski and Maeno, J. Glaciology 39, 645-655, 1993); (ii) the formula for the phase transiti on rate. The experimental results, when extrapolated to lower temperat ures, provide data appropriate for the icy/rocky regolith of satellite s: it is very plausible that the porous regolith layer extended in the past or it extends even now, to the deep interiors of medium size sat ellites (Kossacki and Leliwa-Kopystynski, Planet. Space Sci. 41, 729-7 41, 1993). The kinetics of the phase transitions within the icy compon ent of satellites must influence the convection and differentiation pr ocesses and therefore it is related to the tectonics of satellites.