THERMAL HISTORIES OF THE KOSI SAMPLES

Thermal histories of (H2O, CO2, CH3OH) porous ice/dust samples during KOSI sublimation experiments are presented and interpreted. The histories show the evolution of a steep temperature rise in a top layer dust mantle, the motion of the water ice sublimation front characterized by a temperature of approximately 210 K and by a discontinuity of the temperature gradient, and the faster motion of the CO2 sublimation front with a temperature of approximately 125 K and a second temperature gradient discontinuity. The CO2 depleted middle layer between the dust mantle and the CO2 ice sublimation front developed a convex temperature profile as a consequence of heat transfer by water vapor flow. It is estimated that water vapor flow transferred heat at a rate of approximately half of the insolation while heat conduction through the matrix contributed only about 5% of the insolation to heat transfer. The matrix thermal diffusivity varied from sample to sample between 2 and 13 x 10(-8) m2s-1. The bottom CO2 enriched layer showed a slow continous warming caused by CO2 resublimation to approximately 125 K. The latter temperature is used to estimate a permeability of the sample of 10(-1) m2s-1.