JUPITER MOON MAY HOLD OXYGEN

Wed, 18 Dec 1996 02:28:55 -0500 (EST)
Source: Ndunlks@aol.com

.c The Associated Press

By JANE E. ALLEN

AP Science Writer

SAN FRANCISCO (AP) -- Two scientists who detected hydrogen coming off Jupiter's frozen moon Ganymede think there could be a great deal of oxygen hovering over its surface or locked in its ice -- perhaps as much as on Earth.

Both conclude that given the huge amounts of hydrogen rising from the surface, there should be enough oxygen on the frozen moon to hypothetically create a 10 foot layer of liquid oxygen. One thinks its more likely to be found in liquid form, while the other thinks it likely to be trapped in ice.

At any rate, what's happening on Ganymede could help explain Earth's evolution into a planet capable of harboring life, said Charles Barth, senior researcher at the University of Colorado's Laboratory for Atmospheric & Space Physics in Boulder.

``We want to know how the Earth's atmosphere evolved; how conditions became proper for life to evolve,'' Barth said Monday at the American Geophysical Union's fall meeting. On Ganymede, ``we're seeing the very first process when UV light reacts with the surface.''

Barth theorizes that ultraviolet radiation beating down on Ganymede is breaking down its ice into its components: hydrogen and oxygen.

Hydrogen is light and rises in the moon's weak gravity, while the heavier oxygen remains, he said, possibly to be trapped, bubble-like, in the ice.

``If this process has been occurring for the past 4 billion years since Ganymede was formed, then the moon should have as much oxygen on its icy surface as Earth has in its atmosphere,'' Barth said.

The liquid oxygen theory comes from Louis Frank, of the University of Iowa. He suggested that the pools, with depths of 33 to 330 feet in craters near Ganymede's poles, could mimic a magnetic field around the planet. Scientists recently detected such a field, but most believe it's formed instead by an iron core.

Torrence Johnson, the Galileo project scientist at NASA's Jet Propulsion Laboratory in Pasadena, called the prospect of liquid oxygen pools ``highly unlikely'' because they would need atmospheric pressure to keep from evaporating.

But with so much hydrogen pointing to huge quantities of oxygen, he said there must be some mechanism at Ganymede either to ``bury it, react it with other things or lose it.''

Barth worked with data from an ultraviolet spectrometer carried aboard the unmanned Galileo spacecraft that detected hydrogen escaping from Ganymede's surface. Frank used another instrument that picked up charged hydrogen particles.

The spectrometer did pick up ozone, a form of oxygen on Ganymede's surface, mostly near its poles. And Barth noted that previous ground-based measurements from the Hubble Space Telescope detected molecular oxygen trapped in the ice.

The new observations of escaping hydrogen provide a mechanism for where that oxygen comes from.

Ganymede is the largest moon in the solar system and one that is shaping up more and more like a planet. At 3,269 miles across, it's three-quarters the size of Mars. Its surface temperatures are a minus-186 degrees Fahrenheit.

Galileo passed within 519 miles of Ganymede on June 27.

AP-NY-12-16-96 2043EST


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