The Evolution of the Nucleus Surface in the Context of the Change in the Brightness of a Comet

The paper presents a model of the thermodynamic evolution of the comet nucleus surface.In the proposed approach,we focus on the analysis of the formation of pits visible on the surface of the cometary nucleus.These pits are a consequence of the thermodynamic evolution of both the surface layers and the inner layers of the cometary nucleus.As a result of complex thermodynamic processes,the surface layer is destroyed.A measure of this destruction is the amount of comet material that is thrown into a coma as a result of sublimation.The effect of this process is an increase in the area on which the incident light scatters.Then we can notice a sudden increase in the brightness of the comet,i.e.,its outburst.A measure of the amplitude of a given outburst is the diameter and thickness of the surface layer that has been destroyed.The mechanism of the evolution of the pits was proposed based on the analysis of many photos taken by the Rosetta probe.The obtained numerical values correspond to the actual brightness changes of the Jupiter family comets during their outburst.