Thermophysical properties along Curiosity's traverse in Gale crater, Mars, derived from the REMS Ground Temperature Sensor

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 1 Hz is achieved 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 dust as well as 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 thermal inertias of bedrock-dominated surfaces ( 350-550 J m-2 K-1 s-½) are lower than expected. We use the detailed shape of the diurnal ground temperature curve to infer the effects of lateral mixing of different materials within the sensor footprint, as well as vertical heterogeneity. While results of this forward modeling approach are non-unique, we find surface configurations capable of creating the observed thermal responses that also are consistent with rover imagery. Bedrock thermal inertias isolated by this modeling are 1000-1900 J m-2 K-1 s-½ for mudstone and 700 J m-2 K-1 s-½ for sandstone. This methodology provides a better basis for inferring properties such as rock porosity, cement composition, and degree of cementation from the thermal inertia. These results highlight the advantages of deriving thermophysical properties from ground temperature records well-sampled in local time.