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02 November 1984
Vol 226, Issue 4674

About The Cover

Neutral sodium cloud which accompanies Jupiter's satellite Io is shown at six different orbital phases. These images of the cloud were acquired by Earth-based observations and are shown to scale with Jupiter. Location and size of Io are indicated by the dot within the crossbars; its orbit is indicated by the dashed ellipse. Changes in the cloud's apparent size and shape are largely the result of viewing perspective. See page 512. [B. A. Goldberg, G. W. Garneau, and S. K. LaVoie, Jet Propulsion Laboratory, Pasadena, California 91109] (Time-lapse movie version of the sodium cloud movements will be shown this winter at the National Air and Space Museum, Washington, D.C.)