Sublimation of cometary ices in the presence of organic volatiles II

Evolution of the surfaces of cometary nuclei is determined by the sublimation of ice. The rate of sublimation is commonly calculated using the simple Hertz-Knudsen formula, which should be corrected by a temperature dependent sublimation coefficient αs (Kossacki et al., 1999; Gundlach et al., 2011; Kossacki and Leliwa-Kopystynski, 2014). In Kossacki et al. (2017) the temperature dependence of αs for water ice with acetone and methanol present in comets was analyzed. In this work the influence of propanal at the temperature  ~195-~230 K and formamide at the temperature  ~200-~235 K were investigated. Experiments were performed with slab ice and porous fine-grained ice. It is found, that the presence of propanal reduces the sublimation coefficient at T < 207 K and enhances at T > 208 K. The presence of formamide reduced the sublimation coefficient in the whole investigated temperature range. Porous fine-grained ice sublimed up to four times slower than non-porous one.