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UA scientists celebrate latest Galileo flyby

UA scientists yesterday celebrated the Galileo orbiter's closest-ever flyby of Jupiter's fiery moon, Io - the most volcanic body in the solar system.

Data collected during Sunday's mission will give imaging team scientists their most detailed look yet at Jupiter's innermost satellite.

The encounter was particularly risky, because the orbiter had to pass through a powerful radiation belt around Jupiter before dipping to within 380 miles of Io's surface.

In anticipation of Sunday night's flyby, Galileo project managers released on Friday images of Io that were obtained during flybys earlier this summer.

"It's been called a volcanic wonderland," said Laszlo Keszthelyi, an associate research scientist at the University of Arizona's Lunar and Planetary Laboratory and member of Galileo's Solid State Imaging Team.

Keszthelyi and other UA scientists on Galileo's imaging team have been busy processing and analyzing the new images, which reveal a world besieged by the most intense volcanic activity in the solar system.

While Io's surface temperature is about minus 150 degrees Celsius, it is dotted with volcanoes that spew lava at temperatures exceeding 1,500 degrees Celsius.

"We're looking at lavas that seem to be hotter than anything in the solar system," Keszthelyi said.

NASA's $1.35 billion Galileo Mission to explore the Jupiter system was launched Oct. 18, 1989, aboard the Space Shuttle Atlantis. Galileo entered orbit around Jupiter on Dec. 7, 1995, to begin a two-year primary mission.

The spacecraft is now approaching the climax of its two-year extended Galileo Europa Mission, which was approved by NASA after the primary mission ended in 1997.

Galileo has since returned a wealth of scientific data about Jupiter and its moons.

The images of Io released Friday show several volcanic features that scientists find particularly intriguing.

Included is a pair of features known as Amirani and Maui, which at 250 kilometers long, comprise the longest known lava flow in the solar system.

Keszthelyi said scientists have long debated the dynamics of such lava flows but have never gotten a close enough view of Io to truly see what is happening on the surface. He added that the new high-resolution images will help answer questions about how these features form.

"We never get to see them while they're moving - this is the best chance," Keszthelyi said.

Another of Io's more noteworthy surface features is the Masubi Plume, a fiery column of volcanic material that towers 60 miles above the moon's surface.

"The real exciting thing about the plume in general is that this is an active plume," said Elizabeth Turtle, an associate research scientist with the UA's Lunar and Planetary Laboratory and member of Galileo's Solid State Imaging Team.

Scientists had previously been unable to determine if the Masubi Plume was active because early images made it appear that the plume was switching "on and off," Turtle said.

Turtle said the new images of the Masubi Plume suggest that Io's surface is much more dynamic than was previously thought.

"That's telling us that these regions that are active, move on the surface of Io - you see the same kind of thing in Kilauea, Hawaii," Turtle said. "This tells us that there are changes going on inside Io."

Scientists have determined that Io's intense volcanic activity is caused by its irregular orbit between Jupiter and Europa.

"The reason for it is quite well known - it's tidal heating," said Alfred McEwen, an associate research scientist at the UA's Lunar and Planetary Laboratory, who is also on the Galileo imaging team.

McEwen said Io has an irregular orbital trajectory which causes its crust to rise and fall as the moon moves closer to and farther away from Jupiter.

"It's like kneading a ball of dough, or bending a piece of wire back and forth - it's frictional heat," McEwen said.

According to the NASA's Jet Propulsion Laboratory, the data obtained during the Oct. 10 flyby will be relayed to earth in the next few weeks.

As the Galileo imaging team anxiously awaits the data from the Oct. 10 flyby, they are planning the observation sequence for Galileo's next encounter with Io, scheduled for Nov. 26.

The next flyby will send Galileo even closer to Io at an altitude of 186 miles above the moon's surface.

"We're really only starting to get the new data down," Turtle said. "To see change over a span of months or years is terribly interesting - there's not many bodies in the solar system that that happens on."