Laboratory investigation of thermal conductivity of dust crust models on the ice comet nuclei surfaces

For the purpose of studying the thermal conductivity of comet ice nucleus surfaces dust crust laboratory experiments were carried out on cometary nucleus models. The experiments were carried out under conditions approximating those at heliocentrical distances from 1 to 3 A.U. The ice H2O which contained the particles of quartz, graphite, nickel and organic substances DL-alanin, DL-treonin, L-valin was studied. Dust matrices 5 to 15 mm in thickness formed under the ice sublimation irradiated with a light beam. In most cases the effective thermal conductivity of the matrices which included sublimation products diffused in them was one or two orders less than that of H2O. (author). 2 figs., 1 tab., 10 refs