Thermal histories of the KOSI samples

Thermal histories of ( H 2 O, CO 2 , CH 3 OH ) 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 CO 2 sublimation front with a temperature of approximately 125 K and a second temperature gradient discontinuity. The CO 2 depleted middle layer between the dust mantle and the CO 2 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 × 10 −8 m 2 s −1 . The bottom CO 2 enriched layer showed a slow continous warming caused by CO 2 resublimation to approximately 125 K . The latter temperature is used to estimate a permeability of the sample of 10 −1 m 2 s −1 .