The thermal emission of two palagonitic soils, common visible and near infrared spectral analogs for bright soils on Mars, was measured over the wavelength range of 5 to 25 μm (2000 to 400 cm-1) for several particle size separates. All spectra exhibit emissivity features due to vibrations associated with H2O and SiO. The maximum variability of emissivity is ≈20% in the short wavelength region (5 to 6.5 μm, 2000 to 1500 cm-1), and is more subdued, <4%, at longer wavelengths. The strengths of features present in infrared spectra of Mars cannot be solely provided by emissivity variations of palagonite; some other material or mechanism must provide additional absorption(s). ¿ American Geophysical Union 1995