The Northwest Africa (NWA) 2737 meteorite is the second Martian meteorite has been identified that is composed primarily of heavily shocked dunite. This meteorite has several similarities to the Chassigny dunite cumulate, but the olivine is more Mgrich and, most notably, is very dark and visually brown [1, 2]. Carefully coordinated analyses of NWA 2737 whole rock and olivine separates were undertaken using visible and near-infrared reflectance, mid-infrared emission and reflectance, and Mössbauer spectroscopic studies of the same samples along with detailed petrography, chemistry, SEM and TEM analyses [3]. Midinfrared spectra of this sample indicate that the olivine is fully crystalline and that its molecular structure remains intact. Nearinfrared spectra of NWA 2737 olivine are compared with those of Chassigny and San Carlos in the figure below. The unusual color and spectral properties that extend from the visible through the near-infrared part of the spectrum are shown to be due to nanophase metallic iron particles (npFe) dispersed throughout the olivine during a major shock event on Mars. Although a minor amount of Fe is present, it cannot account for the welldocumented unusual optical properties of Martian meteorite NWA 2737. Apparently unique to the Martian environment, this “brown” olivine exhibits spectral properties that can potentially be used to remotely explore the P-T history of surface geology in addition to surface composition.