Voyager Images -- Page 2

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Enhanced color mosaic of a portion of Io from approximately 0° to 60° latitude and from -60° to 10° longitude. A persistent thermal hotspot named "Kanehekili" is located just north of the rectangular bright orange patch in the upper left quadrant of the scene. Voyager also imaged an active volcanic plume in the vicinity of the large Y-shaped black patch (a lava flow?) at bottom left.

Prometheus, another plume observed by Voyager in 1979, is seen in this triptych of three views taken over a 6-hour span. The Promethus plume extends upward 70 kilometers into space before falling on the surface 125 kilometers from the central vent. The plume somewhat resembles an umbrella, with several prominent dark radial spokes comprised of optically thick concentrations of plume material. The plume may be composed of sulfur dioxide explosively heated within the crust of Io. The first image is a black-and-white image, the second shows the area in approximately natural color, the third view shows the area in enhanced color (emphasizing blues and violets where color difference between geologic units on Io is more pronounced). Prometheus can also be viewed in 3-D. Focus on two adjacent images, and allow your eyes to cross until the two images merge. (Red-green stereo glasses do not work on this image.)

Red-green stereo glasses can be used on this image to see the Prometheus plume in 3-D.

Mountains and plateaus on Io

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Haemus Montes, located near Io's south pole, rise approximately 10 kilometers above the surrounding plains (Mount Everest rises almost 9 kilometers above sea level). The origin of these and other similar mountains, which cover about 2% of Io's surface, is uncertain. They are possible evidence of tectonic deformation predating most of the volcanic material that surrounds them.

Red-green stereo glasses can be used with this image to see Haemus Montes in 3-D.

Ra Patera is the largest shield volcano on Io. Shield volcanos, like Hawai'i, are large volcanic edifices composed of numerous overlapping lava flows. They are called shields because they form broad convex domes with low slopes. Dark linear flows radiate from the center of Ra. Some have speculated that these flows are composed of sulfur, although many do not agree with this interpretation. Ra Patera was not active when Voyager passed in 1979, but Hubble Space Telescope observations in 1995 and 1996 indicate that a major change has taken place at this location, quite likely a major volcanic eruption. Galileo should obtain new images of this area that will hopefully reveal the origin of these changes.