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Galileo spies Io's hot lava, tall mountains

Io volcanoes
These Galileo images show the changes over several months in the lava eruptions from the Tvashstar Catena volcanic pits on Io  

(CNN) -- A NASA probe in the Jupiter system snapped incredible pictures of the hottest volcanoes and some of the tallest mountains in the solar system as it dipped near a fiery jovian moon.

The images, taken as close as 124 miles (200 km), offer new insights into the intense forces that heat, melt and contort the moon's surface, NASA scientists said this week.

The resilient Galileo spacecraft has orbited Jupiter and its moon for five years, surviving more than three times the deadly radiation it was designed to endure.

The observations reveal a world so intensively volcanic that the entire surface likely consists of lava in various stages of cooling, NASA said.

One Io lava field spews forth more than 100 tons of intensely hot sulphurous lava each second, dwarfing the output of its nearest terrestrial rival in Hawaii.

Io has peaks that reach 55,000 feet (17,000 m), almost twice as high as Mt. Everest. Only Olympus Mons on Mars is taller.

Flyover Simulation of Tvashtar Catena Area on Io
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Scientists are intrigued by the size of Io's mountains, which are not volcanic. Considering the intense heat of the surface -- up to 2,800 F (1,538 C) -- they would expect the surface to be liquid or soft with few topographical features.

Planetary scientist William McKinnon speculates that as the crust cools, sinks and then becomes superheated, its breaks up into mountain-forming faults.

"Heat is actually trying to come out from deep in the interior of Io, but the crust is subsiding as new layers of lava are laid down," said McKinnon in a statement. "For this heat, it's like trying to run up a down escalator."

A researcher at the Washington University in St. Louis, Missouri, McKinnon published a report on the matter with colleagues in the February issue of the journal Geology.

Scientists think the Galileo data could shed light on conditions on our planet in the distant past when it was hotter and more geologically active.

Galileo snapped the newly released images during flybys in late 1999 and early 2000. The probe will visit Jupiter's moon Callisto on May 25. The Galileo mission is managed by NASA's Jet Propulsion Laboratory in Pasadena, California.

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NASA's Jet Propulsion Laboratory
More Galileo images of Io
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4:30pm ET, 4/16

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