Thermophysical properties along Curiosity's traverse in Gale crater, Mars, derived from the REMS ground temperature sensor

Abstract

The REMS instrument onboard the Mars Science Laboratory rover, Curiosity, has measured ground temperature nearly continuously at hourly intervals for two Mars years. Coverage of the entire diurnal cycle at 1Hz is available every few martian days. We compare these measurements with predictions of surface-atmosphere thermal models to derive the apparent thermal inertia and thermally derived albedo along the rover's traverse after accounting for the radiative effects of atmospheric water ice during fall and winter, as is necessary to match the measured seasonal trend. The REMS measurements can distinguish between active sand, other loose materials, mudstone, and sandstone based on their thermophysical properties. However, the apparent thermal inertias of bedrock-dominated surfaces (∼350–550Jm−2K−1s−½) are lower than expected. We use rover imagery and the detailed shape of the diurnal ground temperature curve to explore whether lateral or vertical heterogeneity in the surface materials within the sensor footprint might explain the low inertias. We find that the bedrock component of the surface can have a thermal inertia as high as 650–1700Jm−2K−1s−½ for mudstone sites and ∼700Jm−2K−1s−½ for sandstone sites in models runs that include lateral and vertical mixing. Although the results of our forward modeling approach may be non-unique, they demonstrate the potential to extract information about lateral and vertical variations in thermophysical properties from temporally resolved measurements of ground temperature.