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Galileo images reveal super-hot lava on Jupiter's moon Io

July 2, 1998
Web posted at: 8:56 p.m. EDT (0056 GMT)
Picture of Io with dark patches showing recent volcanic activity  

TUCSON, Arizona (CNN) -- Lava erupting from volcanoes on Jupiter's moon Io is hotter than any lava eruptions on Earth today, scientists said Thursday.

Researchers at the University of Arizona at Tuscon studied infrared images of 12 different "hot spots" on Io, which is about the same size as the Earth's moon. The findings were published in this week's edition of the journal Science.

New analysis of the photos from the spacecraft Galileo reveals that Io's lava reaches temperatures of 2,600 to 3,140 degrees Fahrenheit. Molten lava comes out of the Earth's volcanoes at about 2,000 degrees Fahrenheit.

'It looks like a pizza'

"The active volcanoes are even hotter than we expected and hotter than any volcanic activities on Earth," said planetary geologist Alfred McEwen, who led the study.

"They are the highest surface temperatures in the solar system other than the sun itself."

Yet surface temperatures on the rest of Io, which is 1.2 billion miles from the sun, stay an icy 243 degrees below Fahrenheit.

Images from Galileo show the moon to be mostly bright yellow with patches of glowing red and black spots covering the surface, said Michael Carr of the U.S. Geological Survey, who worked on the study. "It looks like a pizza."

Although lava temperatures on Earth are lower, studying volcanic activity on Io offers clues to how similar eruptions shaped the Earth 2.5 billion years ago, said planetary geologist Sarah Fagents.

"The early Earth had a much higher heat flow than we have today," McEwen said. "This could be important in understanding what the Earth was like in (the) early Precambrian (period)."

Astronomers first learned of active volcanoes and lava flows on Io in 1979, when the Voyager spacecraft flew by. At the time, the Voyager images indicated that the lava was much cooler, at about 710 degrees Fahrenheit.

Why so hot?

Today, geologists still know little about the terrain of Io and don't know exactly why the moon's lava is so hot.

Scientists say that because Io is in a non-circular orbit around Jupiter, its shape changes as it move closer to and farther from the planet. This "flexing" causes friction beneath the surface, leading to hotter temperatures, McEwen said.

Other scientists speculate that magnesium-rich silicates result in the much higher temperatures.

Reuters contributed to this report.

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