Tests on the Thermal Conductivity of Regolith Quasi-Analogues at Different Porosities

Knowledge of the thermal conductivity of the regolith is required both for the design and the interpretation of in-situ experiments in future missions to Moon and planets. A variety of available analogue soil material, intended to mimic extraterrestrial soils, have been considered in a series of laboratory experiments. They cover a broad range of finer grained silty sands to coarse sands. Thermal conductivity was determined by the standardized transient procedure using a needle probe at different porosities under ambient room temperature. A steady-state method based on the divided bar technique was used for verification purposes. The results show for all types of soil examined the expected reduction of the thermal conductivity with increasing porosity. Comparisons demonstrate that the use of solely the grain size distribution curve as the relevant characteristic to model the response of this type of granular media is not appropriate. A material-specific, linear variation of conductivity with porosity as derived from the test results is given in the paper.