Thermal conductivity of planetary regoliths: The effects of grain-size distribution

The thermal properties of a planet's regolith are of primary importance in solar system exploration. Thermal conductivity and the related parameter thermal inertia are often used to decipher the regolith's structure, grain size, and areal distribution. In this work we utilize a guarded-heat-flow apparatus to measure the thermal conductivity of mono-dispersed and bimodal size populations of regolith analogs (borosilicate-glass beads and terrestrial soils) under a range of interstitial gas pressures from 10−5 to 103 mb, at 20 °C. From these measurements we further develop a physically based analytical model for use as a predictive tool for planetary research.