SPACE.com -- Galileo Captures Turbulant Jovian Moon Io in Action

When Galileo flew near the south pole of Io in October 2001, scientists targeted this cliff to study the process of erosion. Water and wind cause most erosion on Earth, but Io has neither surface water nor an atmosphere. The cliff is slumping due to gravity.

New and older lava flows clustered in the Tvashtar region of Jupiter's moon Io appear as hot spots in a temperature map from NASA's Galileo spacecraft. The multiple hot spots indicate continuing shifts in the location of Tvashtar's eruptions since the region's volcanic activity was first seen in December 1999.

High temperatures observed by NASA's Galileo spacecraft along the western edge of the Loki volcano on Jupiter's moon Io may indicate freshly exposed material at the shore of a lava lake. Two temperature maps of the southern portion of Loki show hot (lower right) and hotter (upper right) features based on infrared-wavelength observations.

In a high-resolution view from NASA's Galileo spacecraft, the Pele hot spot on Jupiter's moon Io shows a complex pattern of areas glowing in the dark, including areas likely to be fresh overturning of a lava lake's crust.

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	Galileo Captures Turbulant Jovian Moon Io in Action By NASA/JPL posted: 04:09 pm ET 27 November 2001

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A slumping cliff, migrating eruptions and churning lava lakes appear in new images of Jupiter's sizzling moon Io from NASA's Galileo spacecraft.

A high-resolution view of a cliff named Telegonus gives information about erosion on a world that has neither surface water nor wind. The cliff is slumping outward due to gravity.

The Tvashtar area on northern Io, where no volcanic activity was seen prior to December 1999, now has a cluster of hot spots. An infrared mapping image from Galileo's Aug. 6, 2001, flyby of Io shows that the surface within the Tvashtar area is hot at the sites observed in 1999 and 2000, as well as at newly observed sites. "The most explosive phase of the Tvashtar eruption may have ceased, but these observations reveal that the area is still active," said Dr. Rosaly Lopes, a volcanologist at JPL. Tvashtar appears to be an example of a volcanic site where activity starts vigorously then gradually declines, similar to many eruptions on Earth, she said.

Io's most powerful volcano, Loki, offers a contrasting style of eruption. The Loki hot spot brightens and fades over periods of several months, possibly in periodic cycles, a pattern not known on Earth. Scientists have proposed that Loki is either an active lava lake or a caldera whose floor is flooded by frequent lava flows.

Infrared mapping images of Loki from Galileo's Oct. 16, 2001, flyby of Io weigh in favor of the lava lake interpretation. They show a concentration of high temperatures along one edge, like a glowing shoreline. This suggests that hotter lava from underneath is showing through where a cooler lava crust is breaking up as it hits the crater wall. High-resolution nighttime pictures of another of Io's hot spots, Pele, also show the apparent overturning of cooler crust on a lava lake.

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