COMPARISON OF LABORATORY EMISSION-SPECTRA WITH MERCURY TELESCOPIC DATA

Thermal emission spectra from four locations on Mercury's surface are compared with three new laboratory emission spectra: two spinels (gahn ite and magnetite) and one carbonaceous chondrite (Allende), The miner al and meteorite choices were made to investigate previously suggested unique scenarios for the evolution of Mercury's surface. No resemblan ce of the Mercury data were seen to the measured emission spectra, We also compare Mercury spectra to a selection of inverted reflectance sp ectra of feldspars, feldspathoids, Apollo 16 lunar breccias, nepheline -bearing alkali syenite, and simple two-component Linear mixes of feld spars and pyroxenes, The Mercury spectra obtained from locations cente red near 40 degrees and 45 degrees mercurian longitude and equatorial latitudes are concave upward in shape between 8 and 10 mu m like that of nepheline but the emissivity maxima of the data occur at shorter wa velength than any of the feldspathoids (nepheline, leucite, sodalite). A good match of the wavelength position of Mercury's emissivity maxim a is provided by the nepheline-bearing alkali syenite. Comparisons to several feldspars in the plagioclase series, and plagioclase and pyrox ene lunar breccia (67031 and 67455), and linear mixing models of plagi oclase and pyroxene provide good matches to some features near similar to 120 degrees and similar to 34 degrees mercurian longitude and equa torial latitudes, More conclusive interpretation of these data from Me rcury requires laboratory studies of emission spectra obtained specifi cally for thermal and insolation conditions appropriate for airless bo dies, (C) 1998 Academic Press.