What is the difference between the nucleus of a comet and its core?
The nucleus of the comet is its solid part that is embedded in a cloud of gas and dust called the coma. The term arises from our perception of the comet as an observational phenomenon, of a fuzzy ball of light with a tail. The nucleus would then be the center of the phenomenon. Until 1986 when the Giotto spacecraft flew past Halley’s comet, we had never seen the nucleus of any comet. Now that we can get close to a comet and study it in more detail, we start to talk about the parts of a nucleus going into its interior. We ask if there is a ‘crust’ of the nucleus which is the top layer that has been processed by devolatilization (the removal of icy materials). Is there a ‘mantle’, which is a layer that is denser than the crust. Since the layering implies some processes involving heat and alteration of material, we then can hypothesize a cometary ‘core’, which is the very center of the solid part of the nucleus. We don’t know the nature of the crust, mantle or core of the comet or even if
