The thermal structure of Martian soil and the measurability of the planetary heat flow

Abstract

We investigate the influence of the external temperature forcing given by seasonal, interannual, and climatic temperature changes on the surface heat flow of Mars and determine how meaningful measurements of the internal planetary heat flow can be obtained. The influence of seasonal temperature changes is found to be efficiently removed if measurements are extended over the period of at least a full Martian year. Interannual variability due to, e.g., eolian-driven surface albedo changes typically alters the heat flow by less than 15%, although errors may be larger if the soil's thermal conductivity and the albedo variations are both large. Heat flow perturbations caused by long-term climatic changes are found to stay below 15%. In order to also determine the soil's thermal conductivity with an accuracy of 20% or better, a direct conductivity measurement is required. We conclude that a measurement of the Martian planetary heat flow is possible with an accuracy of 30% or better if measurements are extended over the period of at least a full Martian year and thermal conductivity is directly measured. Temperature sensors should have a precision of 0.1 K, and measurements should be conducted up to a depth of 3–5 m.