![]() McEwen and other researchers have been analyzing the new images, and are describing some of their observations during meetings of the American Astronomical Society's Division of Planetary Sciences conference in Pasadena, Calif., this week. "It's gratifying to see Galileo continuing to provide us with new discoveries after enduring more than three times the radiation dosage it was designed to handle," said Duane Bindschadler, manager of Galileo's science planning and operations team at JPL. To approach Io, the spacecraft had to enter a region of hazardous radiation around Jupiter. Galileo took the images during a flyby that passed within 199 kilometers (124 miles) of Io in February, and transmitted them to Earth during the following eight months. The new images of Io are available online from the Jet Propulsion Laboratory, Pasadena, Calif., at and from the UA Lunar and Planetary Laboratory in Tucson, Ariz., at New images also add evidence that many bowl-shaped depressions in volcanic areas may be linked to fracturing and shifting of Io's crust, not just to collapses above underground magma chambers, like the large volcanic craters called calderas on Earth. "We'd like to know where it is coming from, how the surface layer is being resupplied." "It looks like this volatile material is sublimating or eroding away by some means, yet it's still there," McEwen said. The textures on Io's plains suggest that some material that had been solid has dissipated by sublimating from a solid to a gas. On Io, it can be either a solid or a gas at the surface, or a subsurface liquid. It includes sulfur dioxide, and probably other sulfur-rich substances, he said. "We see this volatile material everywhere on Io where we've had a close-up look," McEwen said. In some of Io's active volcanic plumes, the volatile material apparently even falls to the ground as frozen particles or crystals, like snowflakes. Alfred McEwen, a planetary scientist at the University of Arizona, Tucson. It's not frozen water like Earth's snow, but a sulfur-rich material that looks like white snow, said Dr. Elsewhere on Io, plains appear fully blanketed by the snow-like material. A bumpy plain in that image has dark and light patches interspersed like dark rocks reappearing through a shrinking layer of springtime snow. The images from NASA's Galileo spacecraft include the highest-resolution view yet of Io, one of Jupiter's large moons. New pictures of the most volcanically active world in our solar system show it also has surface activity that resembles the accumulation and disappearance of bright snow or ice.
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