Thermal infrared emission spectra of the Moon and Mercury have been obtained using the Si:As photoconductor and circular variable filter (CVF) at the NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii. Lunar spectra from 7.2 &mgr;m to 12.2 &mgr;m for two different locations in the south polar highlands have Christiansen frequency peaks at 8.1 &mgr;m and 7.9&mgr;m respectively. This indicates different compositions at the two locations; mafic in the first case, more felsic in the second. Emission spectra from Mercury are not as spatially localized; however the longitude of maximum contribution to the spectrum can be calculated from thermal models of the earth-facing disk. Results for areas centered at two longitudes have been obtained so far. Two locations in the intercrater plains were observed. At 40¿ longitude (very near the crater Homer), a peak at 7.9 &mgr;m indicates mafic igneous rock type. One day later, spectra emanating from 46¿ longitude have peaks at 7.8 &mgr;m and indicate a region borderline between mafic and intermediate composition. ¿ American Geophysical Union 1988