The thermal inertia of Mars from the Mars Global Surveyor Thermal EmissionSpectrometer

We have used Mars Global Surveyor (MGS) Thermal Emission Spectrometer therm al emission measurements to derive the thermal inertia of the Martian surfa ce at the similar to 100-km spatial scale. We have validated the use of nig httime-only measurements to derive thermal inertia as well as the use of a single wavelength band versus bolometric thermal emission measurements. We have also reanalyzed the Viking Infrared Thermal Mapper data set in a simil ar manner in order to allow a direct comparison between the two. Within the uncertainties of the fit of the data to the model, and the uncertainties i nherent in the model, the thermal inertia has not changed substantially in the 21 years between the Viking and the MGS measurements. Although some dif ferences are seen, they are most likely due to changes in albedo during the intervening years or to residual effects of airborne dust that are not ful ly accounted for in the thermal models. The thermal inertia values that we derive, between about 24 and 800 J m(-2) s(-1/2) K-1, are thought to better represent the actual thermal inertia of the Martian surface than previous estimates.