English: While hunting for volcanic plumes on the volatile moon Io, the Hubble Space Telescope captured this image of Io sweeping across the giant face of Jupiter and casting its shadow below.

The smallest details visible on Io and Jupiter measure 93 miles (150 kilometers) across, or about the size of Connecticut. The bright patches on Io are regions of sulfur dioxide frost. On Jupiter, the white and brown regions distinguish areas of high-altitude haze and clouds; the blue regions depict relatively clear skies at high altitudes.

The image was captured with Hubble's Wide Field and Planetary Camera 2 on July 22, 1997.

For more information, visit: hubblesite.org/news_release/news/1999-13

Credit: John Spencer (Lowell Observatory) and NASA