Galileo’s close-up view of a massive volcanic eruption on Io.

By Keith Cowing
December 21, 1999
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Galileo obtained highly detailed images of a volcanic plume during its close pass to Io on 25 November 1999. Volcanic plumes were first detected on Io during the Voyager flyby in 1979. Subsequent imagery and analysis by Voyager 2 and Galileo have added significant information – yet – until now – none of the images obtained has shown such close up detail. With added observations by Earth-based telescopes, scientists have managed to obtain their best-yet understanding of how volcanoes operate on Io.

According to NASA JPL “[Earth-based] telescope observations show that [the volcano] Loki began a period of major eruption in early September, and Galileo caught the eruption in full force during its October flyby of Io. While observing Loki’s 120-mile (193-kilometer) wide caldera, one Galileo instrument found a sharply defined region that was much hotter than the rest.”

With regard to the imagery obtained by Galileo, NASA notes that: “this image shows a fountain of lava spewing above the surface of Jupiter’s moon Io. The active lava was hot enough to cause what the camera team describes as “bleeding” in Galileo’s camera, caused when the camera’s detector is so overloaded by the brightness of the target that electrons spill down across the detector. This shows up as a white blur in the image. “

° Galileo Sees Dazzling Lava Fountain on Io, NASA press release

° The latest images from Io, NASA JPL

° Close-up montage of volcanic plume on Io, Planetary Photojournal, NASA JPL

° Lava Fountains in Giant Calderas- Interpretation, Planetary Photojournal, NASA JPL

° Galileo home page, NASA JPL

° NASA Infrared Telescope Facility, Mauna Kea, HI

° Lunar and Planetary Laboratory, University of Arizona

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