Abstract

The thermal response of the martian subsurface due to solar forcing lacks direct measurements. The InSight mission provides the best opportunity to detect the thermal behavior of the subsurface since it was equipped with both air temperature sensors and a subsurface heat flow probe. Here, we model heat conduction under the InSight landing site based on the measured subsurface thermal parameters and air temperature records, which provide insights into heat flow in the martian subsurface. Daily temperature variation over 1 K occurs only within 25 cm under the ground surface. The highest absolute rate of temperature change appears around sol 440, which coincides closely with the season of the dominant number of marsquakes observed around sunset. Thermal-mechanical finite-element method simulations indicate that more potential afternoon marsquakes might exist but be covered by the wind noise. Our results indicate that most high-frequency and low-magnitude marsquakes are likely thermal in origin.