Topography formation driven by sublimation of pure species on icy airless worlds

Abstract

Sublimation can drive morphologic changes on the surfaces of icy, airless worlds; the magnitude of these changes depends sensitively on their surface shape, subsurface geology, and volatility of the ice species present. To predict the steady-state and stability of the surface, we examine the molecular transport conditions and their constraints for several pure species sublimating from irregular surfaces in a free-molecular regime subject to variations in thermal conditions at or near the surface. We find that the temperature difference, ΔT∗ between the high and low points on the surface required for morphological instability changes of a given surface geometry increases as the volatility of the ice species increases. From Figure 4, for k=1 and Ts=150K, ΔT∗ is about 3K for H2O and 5K for CO2. Furthermore, we developed an analytical relationship between the saturation vapor pressure of a pure species, its surface geometry and temperature profile, and the required molecular transport conditions.