![]() ![]() ![]() To put this in perspective, the very best images from Voyager had 500 m resolution. "For the October flyby we'll be targeting four major volcanoes," says JPL's Duane Bindschadler, the manager of Galileo's Science Planning and Operations Team, "Pillan Patera, Prometheus (the most prominent one on the surface), Loki, and Pele. In November Galileo might even pass through the plume of Pillan Patera, making it the first spacecraft ever to fly through an alien volcano. What makes the lava around the volcanic vents so incredibly hot? What are the plumes made of? What causes the many colors of Io's mottled surface? Scientists hope that these and many other questions will finally have answers after Galileo makes two daring passes less than 620 km above Io on October 11 and November 25, 1999. Although this process is fairly well understood, many aspects of Io's forbidding environment remains a mystery. The intense volcanism on Io results from 100 meter high tides raised in its otherwise solid surface by nearby Jupiter and the other Galilean satellites. November 30: Learning how to make a clean sweep in space In fact, if you put Old Faithful on Io it would be about 37 km high!"ĭecember 3: Mars Polar Lander nears touchdown We call this the 'stealth plume hypothesis.' The closest Earthly analog to what's happening would be a water geyser like Old Faithful. On a previous flyby the Particles and Fields instruments saw a deficit of energetic particles over Io where gas was probably coming out of the surface - but no plumes were seen. "The volcanic plumes get most of the attention but there are probably also things like fumeroles and geysers. "Io has lots of thermal areas just like Yellowstone," says JPL's Bill Smythe. Bright red materials (such as the prominent ring surrounding the currently erupting plume Pele) and spots with low brightness or albedo ("black" spots) mark areas of recent volcanic activity and are usually associated with high temperatures and surface changes. Sulfur dioxide is normally a gas at room temperatures, but it exists on Io's surface as a frost after condensing there from the hot gases emanating from the Io volcanoes. Deposits of sulfur dioxide frost appear in white and gray hues while yellowish and brownish hues are probably due to other sulfurous materials. The area shown is 11,420 kilometers in width. Above: This false color infrared composite of Jupiter's moon Io was produced from images acquired in July and September, 1996 by NASA's Galileo spacecraft. ![]()
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