- MADISON, Wis. (AP) -- More than 30 volcanoes spew lava, an eerie blue
light erupts from torrid fountains and a natural dynamo generates more
electricity than every U.S. power plant combined.
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- That's Io, a moon of Jupiter that is
sort of an energy hell.
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- New photos from the Galileo satellite
show lava glowing in red pools, scattered like an angry rash across the
face of Io.
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- There is a bluish color from some eruptions,
and, in black space just above, there is an arc of light generated by power
surges estimated at more than 400,000 volts.
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- It all comes from a combination of volcanism,
magnetic field generation of power and the enormous gravitation forces
of Jupiter, Io's mother planet, said Paul Geissler of the Jet Propulsion
Laboratory.
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- Tidal forces from Jupiter twist and contort
little Io, creating frictional heat that erupts in at least 32 volcanoes,
he said.
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- "Io is the most volcanically active
body in the solar system," Geissler said Tuesday at a meeting of the
planetary division of the American Astronomical Society.
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- There is enough lava flowing every year
on Io, said Geissler, to cover the entire surface about one centimetre
deep. For this reason, the little moon is the only major body known in
the solar system to have no evidence of asteroid craters. The lava erases
the impact mark, he said.
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- Pillon, a major Io volcano, spews lava
that is about 1,420 degrees C, hundreds of degrees hotter than volcanoes
active on Earth, said Geissler.
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- As it orbits Jupiter, Io intersects powerful
magnetic field lines from the giant planet and acts like an enormous electrical
generator. This natural dynamo creates more than a trillion watts of power.
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- The power causes Io to glow when it is
in the shadow of Jupiter. Pictures from Galileo show the moon with a glimmering
halo.
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- Near the surface, the combination of
electricity and gases from the volcanoes create an even more unusual sight,
said Geissler. Sulphur dioxide venting from the volcanoes is energized
by the charged particles from the electrical fields. The gas then glows
in a brilliant blue.
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- Io also has fields of red and green,
generated when charged particles energize molecules of oxygen and hydrogen
and other gases.
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- "This light show has been going
on for a billion years," said Geissler, "and this is the first
time it has ever been seen."
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- Galileo, orbiting Jupiter and its moons
for 2 1/2 years, will continue taking photos of the planet and its satellites
for at least another year.
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- Io is 3,600 kilometres in diameter, slightly
larger than the Earth's moon.
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- Io is one of four Jupiter satellites
or moons discovered by Italian astronomer Galileo Galilei, one of the first
astronomers to study the heavens with a telescope. The other major moons
are Gannyede, Europa and Callisto. Jupiter has at least a dozen smaller
moons.
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