Thermal inertias with spatial resolutions as small as 2 by 5 km were combined in a regional study of the Elysium and Aeolis quadrangles of Mars (30¿ N to 30¿ S, 180¿ W to 225¿ W). The range of thermal inertias obtained was 1--14 (X 10-3 cal cm-2 s-1/2 K-1=41.84 j m-2 s-1/2 K-1), with the lowest values corresponding to the Elysium Rise and the highest values correlating with dark patches of aeolian material in the southern highlands. The thermal properties obtained from the high spatial resolution measurements are essentially identical to the results obtained from data with much poorer spatial resolution, indicating a regional homogeneity of surface properties at scales greater than 5 km. Aeolian features, both dark patches and bright materials associated with topographic obstacles such as craters, have higher thermal inertias than do their surroundings.

Other surface features do not display distinctive thermal properties, even when clearly resolved from their surroundings. Comparison of the thermal inertias with global data sets show a pronounced inverse correlation with albedo (consistent with globally observed trends) and brightnesses at red, green, and violet wavelengths but no prominent correlation with elevation. Thermal inertias for individual geologic units within the two quadrangles appear to be more strongly controlled by the location of the terrain in either the northern plains or the southern highlands than by properties intrinsic to the unit. ¿ American Geophysical Union 1987