Seasonal Variations of Soil Thermal Conductivity at the InSight Landing Site

Abstract

Thermal conductivity is a fundamental parameter that governs heat transport in planetary soils. For atmospheric pressures of a few mbar like those typically encountered on Mars a strong dependence of soil thermal conductivity on atmospheric pressure is expected for unconsolidated soil with grain sizes between a few tens of µm and a few mm. In contrast, conduction through the gas phase becomes less important when the soil is cemented or indurated. To study the relative importance of different heat transport mechanisms in the martian soil, measurements at different atmospheric pressures are needed. In this way, the contributions of grain-to-grain conduction as well as conduction through the pore filling gas can be separated. Here we report on the first in-situ long term monitoring of soil thermal conductivity on Mars as obtained by the Heat Flow and Physical Properties Package (HP3) on the InSight mission.