Thermal Inertia at the MSL and InSight Mission Sites on Mars

Abstract

For planetary surface materials, thermal inertia is the critical property that governs the surface’s daily thermal response and controls diurnal and seasonal surface temperature variations. Here we use the ground measurements made by the MSL Curiosity rover and the InSight lander to determine the thermal inertia of two sites on Mars. This study compares the variation of thermal inertia during and after the Large Dust Storm (LDS) of Martian Year (MY) 34. To determine surface thermal inertia, we derive a simple approximation (using energy balance), which utilizes surface albedo, surface energy flux, and diurnal change in the surface temperature. The average thermal inertia in MY34 is about 39.2%, 3.7%, and 3.4% higher than MY35 average thermal inertia for the MSL, InSight (FOV1), and InSight (FOV2), respectively. Notably, the thermal inertia at the InSight (FOV1) is consistently lower by about 20 J·m^–2·s^–1/2·K^–1 than the InSight (FOV2) site for all scenarios, indicating variation in the region’s surface composition. The best-fit surface albedo in MY34 (determined using the KRC model) are about 0.08, 0.05, and 0.03 higher than MY35 surface albedo for the MSL, InSight (FOV1), and InSight (FOV2), respectively. An increase in both surface albedo and thermal inertia during the LDS indicates that the underlying surface is both more thermally resistant and more reflective than the overlying loose dust.