- Scientists have detected new evidence
of underground oceans on two of Jupiter's moons, Europa and Callisto, boosting
hopes of finding life in seemingly inhospitable places in the solar system.
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- "One could expect life in such oceans,"
said Krishan Khurana, a geophysicist at the University of California at
Los Angeles and lead author of the research published Thursday in the journal
Nature.
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- Heat and water in liquid form, as opposed
to ice, are considered fundamental requirements for life. The latest findings
were put together by a team from UCLA, the California Institute of Technology
and NASA's Jet Propulsion Laboratory.
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- Ice-encrusted moons like Europa and Callisto,
and other frozen moons even farther from the sun, were long thought to
be too cold for life to form.
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- "If we find out 4 1/2 billion years
after the formation of the solar system that there's still enough heat
that ice will melt on the interior of these bodies, we have to do a little
bit of rethinking," said one of the researchers, UCLA physicist Margaret
G. Kivelson.
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- Earth is 93 million miles from the sun;
Jupiter, 483 million.
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- The scientists hypothesized the existence
of underground seas from data collected by the Galileo spacecraft. Galileo
measured strong disturbances to Jupiter's magnetic field as the spacecraft
zipped past Europa and Callisto.
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- However, the moons lack strong magnetic
fields of their own that could exert such a force. The scientists concluded
that Jupiter's magnetism must be giving rise to secondary fields within
some powerful electrical conductor on each moon -- a phenomenon known as
electromagnetic induction, which is at work on Earth in generators and
electromagnets.
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- The researchers could imagine only one
sufficiently strong conductor that is plausible on those moons: huge bodies
of salt water. They would be within about 60 miles of the frozen surface,
kept from icing over by heat within the interior of the moons. Assuming
they are as salty as Earth's oceans, they would be about six miles deep.
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- "It's making all of us go back to
our models and think about our understanding of these icy bodies,"
said Ronald Greeley, an Arizona State University geologist who studies
moons.
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- Europa was already viewed as a leading
candidate in the search for life, because its jigsaw crust resembles broken
icebergs and thus points to the possibility of oceans at least in the past.
However, Callisto's pockmarked surface contains little visible trace of
liquid movement below.
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- BBC Sci/Tech 10-22-98
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- New hope of finding life on Mars
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- The Red Planet: Water may lie under polar
ice caps
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- Data from a Nasa probe has revealed that
enough heat from inside the Red Planet might be trapped at the poles to
melt underground water ice.
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- This could create lakes below the ice
caps - and where there is water, there could be life.
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- The Global Surveyor probe has also detected
what may be a clathrate - a layer of water surrounding carbon dioxide molecules
under the surface.
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- This would help retain heat and nurture
life.
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- New observations of Jupiter's moon Europa
have also raised hopes of finding water, Nature magazine has reported.
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- When the Voyager spacecraft passed Jupiter
in the 1970s they discovered that Europa - only slightly smaller than our
own moon - was covered in a layer of ice.
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- But because Europa may have a warm interior
it was suggested that between the ice crust and the warm rocks may be an
ocean of warm water.
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- Since the Galileo spacecraft arrived
at Jupiter in December 1995 it has taken many photographs of Europa and
all of them have tantalised astronomers with the possibility of a sub-surface
ocean.
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- Search for life
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- Despite lacking a magnetic field, Europa
seems to disturb Jupiter's strong field, a fact that scientists say is
best explained by water beneath its icy surface.
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- Many scientists now regard Europa - not
Mars - as the most promising place to look for life off the Earth. There
are plans to send a probe to orbit the moon.
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- The proposal is to land on its surface
and use hot water to melt a way through the ice crust and emerge into the
dark ocean below - to begin a search for life.
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