To verify the quality and accuracy of Phobos-2 ISM spectra of Mars, we have performed comparisons with telescopic data obtained contemporaneously and which have spatial and spectral overlap with the ISM measurements. We find general agreement between the independently-calibrated data sets in terms of spectral shape and absorption band strength and position in the 0.77 to 0.93 &mgr;m overlap region. The telescopic data were scaled to the ISM reflectance values in this overlap region to yield new bright and dark region composite reflectance spectra from 0.40 to 3.14 &mgr;m. We ascribe the increase in band depth and overall spectral heterogeneity of the ISM data relative to previous telescopic observations to the more than order of magnitude increase in spatial resolution achieved by ISM from Martian orbit. Further increases in spatial resolution from future orbital imaging spectroscopic instruments can be expected to reveal even greater degrees of compositional and mineralogic diversity on Mars.