ChangE-4 Measurements of Lunar Surface Temperatures: Thermal Conductivity of the Near Surface Regolith

Lunar thermal conductivity is significantly important for understanding the geological processes of the Moon. The Apollo in situ heat flow experiments and diviner remote sensing data provide us with good constraints on the thermophysical properties of the lunar regolith fines layer. As the first farside in situ experiments, Chang'E-4 (CE-4) temperature sensors will further extend our understanding. In this study, a 1-D thermal model with updated bulk densities by the CE-4 lunar penetrating radar (LPR) data is used. Then, the nighttime surface temperatures from the sensors of the CE-4 lander are applied to retrieve the surface thermal conductivity at the CE-4 landing site. After minimizing the differences between the predicted temperature and CE-4 measurements, the range of surface layer contact conductivity ( ks) within the upper 1 cm is about (0.95-2.26) x 10(-3) Wm(-1) center dot K-1 for T1, (1.04-2.44) x 10-3 Wm(-1) center dot K-1 for T2, (0.60-1.40) x 10(-3) Wm(-1) center dot K-1 for T3, and (0.60-1.39) x 10(-3) Wm(-1) center dot K-1 for T4, respectively. In addition, the factors that may affect the inversion or the measurements were discussed, such as the shadowing effect, the rock abundance (RA), the lateral conduction from the rover transfer mechanism, and the densification effect during the measurements.

Automated summary

In this study, a 1-D thermal model with updated bulk densities is used to calculate the surface thermal conductivity of the Moon based on the temperature sensor data and measurements from the Chang'E-4 lander. The results show that the range of surface layer contact conductivity is (0.95-2.26) x 10(-3) Wm(-1) center dot K-1 for T1, (1.04-2.44) x 10-3 Wm(-1) center dot K-1 for T2, (0.60-1.40) x 10(-3) Wm(-1) center dot K-1 for T3, and (0.60-1.39) x 10(-3) Wm(-1) center dot K-1 for T4, respectively. Factors such as the shadowing effect, rock abundance, lateral conduction, and densification effect during the measurements were also discussed.