Galileo Takes a Closer Look at Io
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Galileo Takes a Closer Look at Io New pictures of Jupiter's exotic moon were captured
on July 3, 1999, as Galileo passed within 81,000 miles of Io.
August 27, 1999: Jupiter's exotic moon Io is often likened
to a pepperoni pizza. Its mozzarella-colored surface is pockmarked
by ruddy volcanic plumes that evoke images of sliced Italian
sausage among imaginative scientists. The strange appearance
of Io's surface is constantly changing as it is formed and reformed
by lava flows of molten silicate rock. What drives this volcanic
powerhouse? The most likely energy source is changing gravitational
tides caused by nearby Jupiter.
Right: This image of Io, captured by Galileo on July 3, 1999 from a distance of 81,000 miles, is color balanced to show how that moon would look to the human eye. [more information]
On July 3, 1999 Galileo flew closer to Io than it has since entering orbit around Jupiter in 1995. During the encounter the spacecraft captured images with a resolution of only 1.3 km per picture element, giving scientists a detailed view of Io's surface.
The color image above was created by combining data from near-infrared, green and violet filters in the spacecraft's camera to approximate what the human eye would see when looking at Io. Comparison of this image to previous Galileo images reveals many changes due to the ongoing volcanic activity. A higher contrast, false color version (below) shows many small-scale volcanic features which were not recognized previously.
Above: This false color image shows
small-scale features which were not recognized previously and
which suggest that the lava and sulfurous deposits on Io are
composed of complex mixtures (close-up A). Some of the bright,
whitish, high-latitude (near the top and bottom) deposits have
an ethereal quality like a transparent covering of frost (close-up
B). Bright red areas were seen in previous images only as diffuse
deposits. However, they now appear as both diffuse deposits and
sharp linear features like fissures (close-up C). Some volcanic
centers have bright and colorful flows, perhaps due to flows
of sulfur (rather than silicate) lava (close-up D). In this region
of Io, bright, white material can also be seen to emanate from
linear rifts and cliffs.
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Galileo has been orbiting Jupiter and its moons since December 1995. Its primary mission ended in December 1997, but the spacecraft is currently in the midst of a two-year extended mission.
More information about the Galileo mission is available at: http://www.jpl.nasa.gov/galileo/
JPL manages Galileo for NASA' s Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology, Pasadena, CA.Web Links
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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
Taking the Scenic Route to Io -- June 30, 1999. Galileo zoomed by Callisto this morning in the second of four encounters designed to bring the spacecraft closer to Jupiter's volcanic moon 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.
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