Reconciling the Infrared and Microwave Observations of the Lunar South Pole: A Study on Subsurface Temperature and Regolith Density

Abstract

AbstractThe Diviner Lunar Radiometer Experiment on the Lunar Reconnaissance Orbiter and the Microwave Radiometer (MRM) onboard Chang'e‐2 (CE‐2) orbiter performed nearly coincident measurements of the lunar south polar region in 2010–2011. In this study, we reconcile infrared data from Diviner and microwave data from MRM to reveal thermal behavior of lunar regolith at very low temperatures. Assuming a uniform density structure and dielectric properties across the polar region, we retrieve a relative apparent thermal‐gradient map based on radiative transfer model. The result shows apparent thermal gradients in the permanently shadowed regions (PSRs) are much larger than that in non‐PSRs, which implies a systematic difference in thermal conductivity and/or density of lunar regolith in PSRs. We also model surface temperature and microwave brightness temperature over time in PSR and non‐PSR locations. The modeling results at these representative locations and the thermal gradient map confirm that the regolith in the PSRs is consistent with a much lower thermal conductivity and higher porosity than non‐PSRs.