Oct 8, 1999

Galileo has a hot date with Io

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Galileo has a hot date with Jupiter's volcanic moon


NASA/JPL releases new images of Io as Galileo heads for a daring flyby of the solar system's most volcanic world




Galileo image of an Io volcano
October 8, 1999: NASA's Galileo spacecraft is gearing up for a daring Oct. 11 rendezvous with Jupiter's moon Io (pronounced EYE-oh), the most volcanic body in our solar system.

Galileo will swoop down to within 380 miles (612 kilometers) above Io's fiery surface at 1:06 a.m. EDT, snapping the closest- ever pictures of this intriguing celestial body.

Right: A plume of gas and particles is ejected some 100 kilometers (about 60 miles) above the surface of Jupiters volcanic moon Io in this color image, recently taken by NASAs Galileo spacecraft. The plume is erupting from near the location of a plume first observed by the Voyager spacecraft in 1979 and named Masubi. However, during the course of the Galileo tour of Jupiter and its moons, a plume has appeared at different locations within the Masubi region. more information.

"Io is a natural laboratory for volcanoes," said Dr. Duane Bindschadler, Galileo manager of science operations and planning. "By studying Io close up, we'll learn more about how and when volcanoes erupt and why they act the way they do. This may even help us predict the behavior of volcanoes on Earth."


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During the flyby, Galileo's science instruments will study the chemistry, heat distribution, gravity and magnetic properties of Io. For scientists, this thrilling encounter promises to yield a bonanza of pictures and information, but for Galileo engineers, the flyby presents a serious challenge with uncertain results. Io's orbit lies in a region of intense radiation from Jupiter's radiation belts, which could affect the performance of spacecraft systems or even knock out various spacecraft instruments. A mere fraction of the dose that Galileo will receive would be fatal to a human.

"We expect that the spacecraft will survive the flyby, although the radiation may cause its computers to reset or may even cause irreversible damage to critical electronic components," said Wayne Sible, Galileo deputy project manager. "There is a possibility, if enough damage is done to the electronics, it won't survive the flyby. Because of this possibility, we planned the Io encounters for the end of the two-year extended mission. After orbiting Jupiter for nearly four years, the spacecraft has more than fulfilled its mission objectives, so it seems reasonable to take a calculated risk for a much closer look at such a scientifically rich target."
Visit for coverage of Galileo's close encounters with Io, including science news and the latest images of Jupiter's volcanic moon.
Galileo was originally assigned to spend two years studying Jupiter, its moons and its magnetic environment. When that original mission ended in December 1997, it was followed by a two- year extended mission, scheduled to end in January 2000. While spending the past four years near Jupiter, Galileo has been exposed to radiation on an ongoing basis, which has caused some of its instruments to act up.

To prepare for any possible harm caused by radiation during the Io flyby, engineers have designed sophisticated software to help the spacecraft weed out a true crisis from a minor glitch caused by radiation and respond appropriately.


Parents and Educators: Please visit Thursday's Classroom for lesson plans and activities related to this story.

Galileo, the first spacecraft to orbit Jupiter, has revolutionized our knowledge of Jupiter and its moons and has provided thousands of colorful images. Data from Galileo support the premise of a liquid ocean beneath the icy crust of Jupiter's moon Europa, an intriguing prospect since water is a vital ingredient for life. Thanks to information sent by Galileo, scientists know much more about the weather on Jupiter and the composition of its moons. En route to Jupiter, the spacecraft took the first-ever close-up pictures of asteroids, when it photographed Gaspra and Ida, and it returned historic images of the destruction of comet Shoemaker-Levy 9 as its pieces slammed into Jupiter.

If all goes well with the upcoming Io flyby, the spacecraft will make an even more daring approach of Io on Nov. 26 at an altitude of only 186 miles (300 kilometers).


Galileo image of an Io volcano

Above: This set of four images, taken by NASA's Galileo spacecraft, shows a sequence of volcanic activity on Jupiter's moon Io over the last two years. As seen from left to right, the feature called Masubi was observed during Galileos 9th, 10th, 15th, and 22nd orbits of Jupiter. These images show that a plume deposit from Masubi appears in September 1997 and has disappeared eight months later, only to reappear in a different place little more than a year later. The deposit, which originated from a volcanic vent, contains snow rich in sulfur dioxide. more information.

New Io images taken by the spacecraft are available at the following website:

Additional information and pictures taken by the Galileo spacecraft are available at the redesigned Galileo website at this new Internet address:

Galileo was launched from the Space Shuttle Atlantis on Oct. 18, 1989. It entered orbit around Jupiter on Dec. 7, 1995. The Jet Propulsion Laboratory (JPL) manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is operated for NASA by the California Institute of Technology, Pasadena, CA.

 Web Links

Related Stories:

Sulfuric Acid Discovered on Europa -- September 30, 1999. Sulfur from Io's fiery volcanoes may be responsible for a battery acid chemical on Europa with implications for astrobiology.
Io or Bust -- September 16, 1999. Galileo braves extreme radiation as it plunges toward a close encounter with Io's volcanoes.
Divining Water on Europa -- September 9, 1999. As circumstantial evidence for an underground ocean mounts, JPL scientists try an ingenious experiment to look for hexagonal ice crystals on the surface of Europa.
Taking the Scenic Route to Io -- June 30, 1999. What's happening to the small craters on Callisto? That's the mystery scientists were contemplating as Galileo zoomed past Jupiter's pockmarked moon this morning in an orbit-changing maneuver designed to bring the spacecraft closer to volcanic Io.
Turn Left at Callisto -- May 5, 1999. Galileo heads for a daring encounter with Io's volcanoes.
Galileo buzzes Europa -- Feb. 2, 1999. Galileo executes a close flyby of Europa for the last time during the current mission.
The Frosty Plains of Europa -- Dec. 3, 1998. As Galileo returns new images of Europa, NASA scientists prepare to study samples from a potentially similar environment here on Earth.
Callisto makes a big splash -- Oct. 22, 1998. Scientists may have discovered a salty ocean and a possible ingredient for life on Jupiter's moon.
Galileo takes a close look at icy Europa -- Oct 2, 1998. The spacecraft flew within 2300 miles of the mysterious satellite last weekend.
Clues to possible life on Europa may lie buried in Antarctic ice -- Mar. 5, 1998. Exotic microbial forms turn up in ice above Antarctica's Lake Vostok.

Related Sites:

Ice, Water and Fire the Galileo Europa Mission
Galileo home page at JPL, with the latest on Europa, Callisto and Io
Jet Propulsion Laboratory home page
Io from the SEDS Nine Planets web site
Callisto from the SEDS Nine Planets web site
Jupiter from the SEDS Nine Planets web site
Io: The Prometheus Plume Aug. 18, 1997 Astronomy Picture of the Day
Close-up of an Io volcano Aug. 4, 1995 Astronomy Picture of the Day
Sizzling Io July 6, 1998 Astronomy Picture of the Day


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