We can measure thermal inertia by taking temperature measurements of the surface at different times of day. To date, three instruments capable of measuring surface temperature from orbit have flown to Mars, the Viking Infrared Thermal Mapper (Viking IRTM), the Mars Global Surveyor Thermal Emission Spectrometer (TES), and Mars Odyssey Thermal Emission Imaging System (THEMIS). In addition, a rover-based version of TES (Mini-TES) was flown on the Mars Exploration Rovers Spirit and Opportunity, and operated between their landing in 2004 and the global dust storm of 2007, which coated their optics in a thick layer of dust.

One issue with using this approach is that these instruments have a different measurement size, which makes it difficult to directly compare thermal inertia values to one another.