Newspaper article The Christian Science Monitor

A Glimpse of Ganymede Reveals the Face of a Planet Jupiter's Largest Moon Has Ice Quakes, Magnetic Field Series: Close-Up Images of Ganymede Taken by NASA's Galileo Spacecraft during a June 27 Flyby Show Deep Furrows in the Icy Crust and Craters Up to 12 Miles in Diameter., JET PROPULSION LAB/AP

Newspaper article The Christian Science Monitor

A Glimpse of Ganymede Reveals the Face of a Planet Jupiter's Largest Moon Has Ice Quakes, Magnetic Field Series: Close-Up Images of Ganymede Taken by NASA's Galileo Spacecraft during a June 27 Flyby Show Deep Furrows in the Icy Crust and Craters Up to 12 Miles in Diameter., JET PROPULSION LAB/AP

Article excerpt

In a looping, seven-year journey across the solar system, the Galileo spacecraft has arrived at a point 480 million miles from the sun to discover ... California?

Images transmitted by Galileo show that Jupiter's largest moon has planet-like features, including an unexpected magnetic field and an icy surface scored by ridges and troughs that remind scientists of California's San Andreas fault.

Ganymede is a place so cold that ice behaves like rock. Its features in rock-hard ice reflect processes that scientists think are similar to those that shape the crust and cause earthquakes on our own planet.

Ice quakes on Ganymede should be "very similar to what we see in southern California," says Galileo imaging team geologist James Head of Brown University. "You would have a lot of snap, crackle, pop right across Ganymede" when these features form, adds Torrence Johnson, Galileo project scientist at the California Institute of Technology's Jet Propulsion Laboratory (JPL) in Pasadena. JPL manages the Galileo project for the National Aeronautics and Space Administration.

On Wednesday, JPL released the first images taken when Galileo zipped by Ganymede on June 27, coming within 516 miles of the moon's surface. Dr. Head explains that the close-ups of faults, fractures, and impact craters are the kind of evidence geologists need to understand Ganymede's geological history. This gives scientists another place to study what makes planets tick.

"We really get a new perspective on how our {own} planet works," Head says.

Dr. Johnson adds that this typifies the bottom-line payoff of planetary exploration. He explains that geophysicists can form theories of what shapes Earth. But projects such as this one allow them to test their theories on other planetary formations.

On Ganymede, he says, nature has provided just such an experiment. Forces similar to those shaping Earth are at work on the moon. But rock is replaced by ice, and Earth's warmth is replaced by cold. By understanding what goes on in a place like Ganymede, scientists say they will better understand what happens on Earth.

The photographs sent back by Galileo are mosaics made up of four shots. …

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