Spectral reflectance of Martian areas during the 1973 opposition: Photoelectric filter photometry 0.33–1.10 μm

Abstract

Reflectance spectra of 26 Martian areas (200–400 km in diameter) that were measured during the 1973 opposition are presented. They were measured through 25 narrow-band interference filters between 0.33 and 1.10 μm, using a photoelectric filter photometer at the Mauna Kea 230-cm telescope. There were many more bright and dark areas observed than during previous oppositions, and for the first time spectra were obtained of dust clouds and areas of mixed and intermediate albedo. The bright areas and dust clouds were all apparently composed of the same mineralogic unit. The dark area spectra differed substantially from the bright area and dust cloud spectra, and they showed major regional variations. The spectra of mixed and intermediate albedo areas had absorption bands seen in both bright and dark area spectra, and did not display any unique new features: thus they were apparently not compositionally unique, but rather were probably composed of mixtures of high albedo dust and dark area soils.