Io's full disk
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High-altitude ionosphere found at Io by Galileo
News story originally written on October 23, 1996
Scientists participating in NASA's Galileo mission have
discovered that the during its Io fly-by, Galileo spacecraft may
have flown through an ionized region, or the ionosphere. This discovery
suggests that Io's atmosphere is time variable and is made of
volcanic gas raised to very high altitudes.
"Sensors on the spacecraft found a very dense region of
ionized oxygen, sulfur and sulfur dioxide at 555 miles on Io
that must be pumped into that region by Io's relentless
volcanic activity," said Dr. Louis A. Frank of the University
of Iowa, principal investigator on Galileo's plasma science
experiment. "Instead of being swept away by Jupiter's
rotating magnetosphere as anticipated, the ionized gases
surprisingly remain with Io," he said.
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