The surface of the Moon is covered by regolith and its microphysical structure is not only linked to surface processes and regolith evolution, but is also important for in situ resource utilization and mission planning. We aim to uniquely constrain lunar regolith grain size and density stratification for the highlands and to further investigate the latitudinal dependence of regolith properties using remote sensing data. We matched simulated surface and microwave brightness temperatures with Lunar Reconnaissance Orbiter/Diviner and Chang'E-2/Microwave Radiometer measurements. The physical temperatures of the regolith were modeled by applying a microphysical thermal model that more directly simulates physical properties of the regolith, such as grain size and volume filling factor. First, we find that the regolith-density stratification and grain size can only be unambiguously constrained by using both Diviner and Microwave Radiometer measurements due to their complementary wavelength ranges. The global regolith grain radius for equatorial highlands was determined to be 45^ +6 _ -4 ̆pmu m and the bulk density in the deeper regolith layers was found to be 1800^ +70 _ -90 kg m^ -3. Second, the combined analysis of the latitudinal dependence up to ± 80^ ̧irc latitude suggests a decrease in bulk density with increasing latitude. We also show that the previously proposed variation in the solar-incidence-angle-dependent albedo is not compatible with microwave brightness temperatures at higher latitudes.
Bürger et al. (Mon,) studied this question.