A Martian yellow cloud—July 1971
Abstract
A short-term yellow cloud was observed in the southern hemisphere of Mars from July 10 to 22, 1971. The initial cloud was first photographed on the morning limb at 7:45 AM local Martian sun time in the Serpentis-Hellespontus region (315°W; 27°S), 74 Earth days (72 Martian days) prior to the onset of the September major yellow storm. Historical observations from the Lowell Observatory archives indicate that prestorm yellow clouds of limited extent are not uncommon. Positional measurement and photographic differential photometry of the July yellow cloud were possible throughout its entire evolution because Mars was favorably situated and photographic coverage by the International Planetary Patrol was adequate. Maps showing the cloud's initial location, hourly and diurnal behavior, apparent motion, and areal coverage by haze are presented. The similarities between the July cloud and other southern hemisphere yellow clouds are summarized. Its relationships to classical albedo features and Mariner 9 topographic data are discussed. Photographic photometry indicates that the enhanced contrast between the yellow cloud and its surroundings is probably due more to the brightening of the cloud-covered areas than to any darkening of contiguous areas.
- Publication:
-
Icarus
- Pub Date:
- July 1974
- DOI:
- 10.1016/0019-1035(74)90182-1
- Bibcode:
- 1974Icar...22..345C
- Keywords:
-
- Cloud Cover;
- Cloud Photography;
- Color Photography;
- Diurnal Variations;
- Mars Atmosphere;
- Spaceborne Photography;
- Astronomical Photometry;
- Mariner 9 Space Probe;
- Southern Hemisphere