Solid-state greenhouse and their implications for icy satellites

Subsurface heating by sunlight can considerably raise the temperatures of relatively translucent, high-albedo materials. We call this the solid-state greenhouse effect and apply it to the study of planetary surfaces. Of special interest to us in this paper are the frost and ice surfaces found on satellites in the outer Solar System. We compute temperatures as a function of depth for an illustrative range of thermal variables. We find that the surface regions and interiors of these bodies can be much warmer than previously expected. For example, in the case of Europa, thermal metamorphosis of the surface layer is indicated. We identify the solid-state greenhouse temperatures as the relevant temperature to use for the upper-boundary condition for the calculations of the thermal state of the interior. Several mechanisms are identified whereby modest alteration of surface properties can substantially change the greenhouse and force an adjustment of inferior temperatures.