NASA/JPL/GALILEO/PIRL/University of Arizona
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This is one of the many images of Jupiter's Moon Io made by the Galileo spacecraft. Io is the most volcanically dynamic object in the solar system, with some three dozen active volcanoes. Some are nearly twice as tall as Mt. Everest, the highest point on Earth.

Io has no impact craters, which tells scientists its surface must be constantly recycled by the volcanism and is probably no more than a million years old.

This image has been colorized, and the background is Jupiter's clouds. It was taken in 1998 at a distance of about 183,000 miles (294,000 kilometers). Io was discovered on Jan. 7, 1610, by Galileo Galilei. It's about the same size as Earth's Moon.

Io's riot of color result largely from sulfur compounds. [About the colors]

-- Robert Roy Britt

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