The major Martian yellow storm of 1971

Extensive Earth-based photography produced by the International Planetary Patrol has been used to map the positions of brightened areas (clouds) during the 1971 storm on Mars. The mapping was done on an hourly basis from two days prior to the onset of the storm through its twenty-second day. Summaries of these maps are presented to illustrate the changes that take place during the course of a Martian day, as well as the changes from one day to the next. It is shown that the storm goes through a daily cycle of regeneration, although each day it advances farther than it did the day before. The possible influence of Martian topography on the progress of the storm is examined. Comparisons between red- and blue-filter photographs of the storm are presented cartographically and are discussed. Areas most affected by the storm during this period are summarized in Fig. 8.