A comparison of mercurian reflectance and spectral quantities with those of the Moon

We have examined previously published Earth-based telescopic spectra of Mercury with the goal of obtaining clues to the planet's surface composition. The study has three parts. First, because of suggestions that Mercury's crust may be anorthositic, we compare near-infrared spectra of Mercury with spectra of lunar anorthosites. The spectral slopes and lack of strong mineralogic absorption features make the mercurian spectra similar to spectra of lunar anorthosites. Second, we compare albedo quantities for Mercury and the Moon computed from telescopically derived photometric parameters with the laboratory albedos of returned lunar samples. The albedos calculated from the photometric parameters are much lower than those of lunar samples measured in the laboratory. Third, the mercurian spectra are interpreted in terms of the current model for the reflectance of an iron-bearing silicate regolith on an airless body. Recent steps toward quantifying this model permit estimates of the FeO content and opaque mineral abundance of the surface to be made. We find that the mercurian spectra least affected by telluric absorptions imply FeO + TiO₂≈ 4%.