A Martian yellow cloud - July 1971

A number of photographs illustrate the changing appearance of Mars just before and during the early stages of the July 1971 yellow cloud. Photographs from July 23 to 27 show that the cloud activity was essentially over 12 days after the initial disturbance had begun. Studies conducted with the aid of photographic differential photometry are discussed along with measurements regarding 95 multicolor photographic sequences for the cloud's initial location, diurnal behavior, areal coverage, and apparent motion.