These photos of the four Galilean satellites of Jupiter were taken by Voyager 1 during its approach to the planet in early March 1979. Io (top left), Europa (top right), Ganymede (bottom left) and Callisto (bottom right) are shown in their correct relative sizes: Ganymede and Callisto are both larger than the planet Mercury; Io and Europa are about the same size as the Moon. Image processing also preserves the relative contrasts of the satellites.
Image Number: NASA-PIA00012
Credit: Image courtesy of NASA/JPL
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