Thermal behavior of regolith at cold traps on the moon׳s south pole: Revealed by Chang׳E-2 microwave radiometer data

• High resolution of microwave brightness temperature map of lunar pole was created.
• Thermal attenuation coefficient and gradient at cold traps were inverted.
• Effect of water ice content on regolith thermophysical properties was discussed.
• Effect of water ice on subsurface temperature was discussed.

The long-term stability of water ice at cold traps depends on subsurface temperature and regolith thermophysical properties. Based on Chang׳E-2 microwave radiometer data, we have inverted attenuation coefficient, thermal gradient and instantaneous temperature profiles at permanently shaded craters (Cabeus, Haworth and Shoemaker) on the Moon׳s south pole. The nonuniformity of the inverted attenuation coefficient within the craters reflects the inhomogeneous thermophysical properties of regolith. In addition, thermal gradient decreased significantly from the crater walls to the bottoms, which may be caused by scattered sunlight, internal heat flux and earthshine effect. Considering continuous supplement of water ice (with volumetric fraction 0–10%) at cold traps, it changes subsurface thermophysical properties but has little effect on thermal gradient. We also assumed that abundant ice (10%) mixed with regolith, the inversion results showed that the maximum difference of diurnal temperatures between “wet” and dry regolith were no more than 0.5 K. That is, the effect of water ice on subsurface thermal behavior can be neglected.