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Surface ices; Water vapor; Ice formation; Computational methods; Comet interiors
Abstract:
We use a generic thermophysical model to study in detail the formation of water-ice frost in the near-surface layers of comet 67P/Churyumov-Gerasimenko. We show that nightly frost formation is a common phenomenon. In particular, while abrupt landscapes may be conducive to frost formation, they are not a requisite condition. We show that the process of subsurface frost formation is similar to that of the condensed ice layer, or crust, underneath. The sublimation of frost produces regular, enhanced outgassing early in the morning. In the case of 67P, this activity is subordinate to and precedes the daily peak sourced from the ice-rich layers located above the diurnal skin depth. In any case, frost activity should be a nominal component of comet water activity.
