Ultraviolet observations of Mars made by the Orbiting Astronomical Observatory.
Ultraviolet albedos of Mars in the region from 2000 to 3600 A are discussed. When the reflectivity due to the known amount of CO2 on Mars is accounted for, the remaining reflectivity may be used to set an upper limit for the surface albedo. The result disagrees qualitatively with published ultraviolet reflectivities of limonite and carbon suboxide. An alternate interpretation of the observations leads to the conclusion that CO2 comprises at least 60% of the molecular atmosphere of Mars, assuming the remainder to be argon. A comparison of the OAO results with 1969 Mariner ultraviolet data reveals some important areas of conflict. Attempts to detect Mars at wavelengths less than 2000 A were unsuccessful, with only very high upper limits being set.