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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