Galileo spots new volcanoes on Io
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(All images courtesy NASA)
(CNN) -- New close-up images of Io document the presence of
numerous unknown volcanoes and reveal some spectacular geological
changes in familiar ones. Snapped by the Galileo spacecraft,
the new photos indicate the Jupiter moon most likely
possesses hundreds of volcanoes, scientists said this week.
The high-resolution observations, made during Galileo's
closest fly by in February, spotted 10 new volcanoes in a
small region. Previously there were only 81 known
active volcanoes on Io.
Because the distribution of active volcanoes seems consistent
around the moon, Io probably has about 300 of them in all,
said Rosaly Lopes-Gautier, a scientist at NASA's Jet
Galileo observed dynamic changes in some of the known
volcanoes during flybys in October, November and February.
Some smaller ones changed from hot and glowing caldrons
to cool, dim inactive volcanoes within weeks.
Larger ones have remained active for years or decades, based on
observations by Galileo and the Voyager spacecraft, which
traveled through the Jupiter system in 1979.
Io's Loki is the most powerful volcano in the solar system.
Between October and February, hot lava seems to have covered
its caldera, or sunken volcanic crater, which spans a region
half the size of Massachusetts.
The Tvashtar Catena volcano burst into an extraordinary
display in November. It has since waned, as illustrated in
the new pictures, but another eruption of hot lava has taken
The most recent images capture Chaac Patera, a crater with
scalloped edges. Its caldera walls reach about 2.8 km (1.7
miles) high and have a slope of 70 degrees, about twice as
high and steep as much of the Grand Canyon.
"The wall rocks must be very strong to support this
topography," said Alfred McEwen of the University of Arizona,
Tucson, a member of the Galileo imaging team, in a statement.
"Each volcanic center on Io is proving to have unique
One small caldera contains the purest sulfur dioxide on Io,
bright white deposits that could be a frozen layer of sulfur
dioxide ice, Galileo scientists said.
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