Cloud Images from the Pioneer Venus Orbiter

@article{Travis1979CloudIF,
  title={Cloud Images from the Pioneer Venus Orbiter},
  author={L. Travis and D. Coffeen and A. D. Del Genio and J. Hansen and K. Kawabata and A. Lacis and W. Lane and S. Limaye and W. Rossow and P. Stone},
  journal={Science},
  year={1979},
  volume={205},
  pages={74 - 76}
}
Ultraviolet images of Venus over a 3-month period show marked evolution of the planetary scale features in the cloud patterns. The dark horizontal Y feature recurs quasi-periodically, at intervals of about 4 days, but it has also been absent for periods of several weeks. Bow-shaped features observed in Pioneer Venus images are farther upstream from the subsolar point than those in Mariner 10 images. 

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