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Release: Oct. 5, 2001

UI researcher detects volcanic smoke plume at Jupiter's moon, Io

IOWA CITY, Iowa -- In the first observation of its kind, University of Iowa physicist Louis A. Frank recently detected freshly released particles from a volcano at Jupiter's moon, Io, using instruments aboard NASA's Galileo spacecraft.

Space scientists, including Frank, were using the spacecraft to examine Io when a volcano at the moon's surface on Aug. 6 unexpectedly emitted the tallest volcanic smoke plume yet seen. During the pre-planned fly-by of Io, scientists captured images of the plume using Galileo's cameras and identified the site of the volcanic eruption using an infrared mapping instrument. Frank, principal investigator on the Plasma Science Instrument, had an opportunity to collect a sample of the volcanic plume -- thought to be composed of flakes of sulfur dioxide -- as it rose some 300 miles above the surface while Galileo sped past at about 120 miles above Io.

He says that by studying the impact of the particles with the plasma instrument, he and his colleagues will be able to learn more about the temperature and speed of the gas.

"It is simply marvelous that we were able to grab some of the strange snow flakes which were formed by the enormous flow of gas from this volcano," Frank says.

The discovery was surprising because no active volcanic plumes had been observed in the high-latitude regions of Io during the first five years of the Galileo spacecraft's investigation at Jupiter and its moons. As the August fly-by approached, scientists were aware that a previous emission had occurred at the site of another volcano about seven months earlier. However, that eruption gave no hint of the August activity or even that a second volcano was active in the region. Frank says that the discovery was "totally unexpected" and leads scientists to wonder what they may find when Galileo encounters Io on Oct. 16 before making its sixth and final fly-by of Io in January 2002.

In previously published papers on Io, Frank and UI colleague Donald Gurnett, principal investigator on the Plasma Wave Instrument, reported that Jupiter's plasma, or electrically charged gas, flows past Io and creates a plasma wake, similar to the watery wake caused by a boat. They also found that a corresponding empty area on Io's backside is filled with dense, relatively cool ions of oxygen, sulfur and sulfur dioxide shooting out from Io's volcanic surface.

In addition to Frank and Gurnett, UI Regent Distinguished Professor of Physics and Astronomy James A. Van Allen continues to serve the Galileo Project as an interdisciplinary scientist.

Galileo was launched from the Space Shuttle on Oct. 18, 1989 and, after a journey of 2.3 billion miles, arrived at Jupiter on Dec. 7, 1995. The Galileo Probe entered Jupiter's atmosphere, while the Galileo spacecraft continued on its mission to investigate four of Jupiter's larger moons. The Jet Propulsion Laboratory (JPL), a division of the California Institute of Technology in Pasadena, manages Galileo for NASA’s Office of Space Science, Washington, D.C. Additional information about the mission is available online at: