Survivability of amorphous ice in comets depends on the latent heat of crystallization of impure water ice.

This article focuses on the thermal evolution of kilometer-sized cometary nuclei, specifically investigating how the latent heat of ice crystallization—affected by impurities in cometary ice—influences the survival depth of amorphous ice within comets. Using one-dimensional numerical simulations of spherical, pebble-pile comets, the study compares exothermic crystallization (positive latent heat, typical of pure water ice) with endothermic crystallization (negative latent heat, representing impure ice). Results show that for comets with radii greater than 1 km, the amorphous ice mantle depth is about 100 meters in the exothermic case but can exceed 1 km when crystallization is endothermic. The findings suggest that the spatial distribution of ice crystallinity in comet nuclei depends strongly on the latent heat value, which varies with impurity concentration, and that this factor should be considered in models of comet thermal history and activity.