A number of spectroscopic instruments with high resolution and complementary wavelength ranges, including TES, THEMIS, OMEGA, and CRISM, will give an unprecedented wealth of information about the surface of Mars. In order to maximize the utility of these data sets, they need to be joined to provide pan-spectral coverage of the surface of Mars that will give information on different types of absorption processes in surface materials. We have performed a test of this approach using ISM and TES data to provide near-infrared and thermal infrared coverage of the selected regions observed by both instruments. Gridding and registering the two data sets to a common reference allows investigations of regional and global properties of the surface. Here we investigate the variability in the spectral properties of low-albedo regions, particularly Type I (basaltic) and Type II regions, and relate these variations to probably mineralogic composition. ISM and TES data agree on the presence of pyroxenes in Type I regions but may indicate a lack of pyroxene in the Type II material, although this is inconclusive. Type I regions in general appear to be uniform in composition, and surface variations are primarily controlled by mixing with dust. Temporal variations in surface reflectance make analysis of the differences in spectral properties between eastern and western Syrtis Major difficult but indicate that slope differences may not be due to intimate cementing of dark and light materials but rather due to penetrative oxidation of the surfaces of basaltic materials. These results demonstrate that the complementary strengths of multiple wavelength regimes allow greater understanding of surface composition and processes.