Study reveals new evidence of saltwater ocean on Europa
(CNN) -- A spacecraft orbiting Jupiter has provided the strongest
evidence yet that a liquid ocean lies beneath the icy surface of the
jovian moon Europa. The discovery enhances the chances that life could be present there, according to a new report.
Using observations from NASA's Galileo probe, scientists determined
that a body of salty water inside the Jupiter's fourth-largest
moon most likely caused unusual magnetic readings.
The ocean, at least 4.5 miles (7 km) deep, would lie beneath an icy layer with a thickness anywhere from .5 miles (.8 km) to 6 miles (10 km), said Margaret Kivelson of the University of California, Los Angeles, lead author of the report published Friday in the journal Science.
| MESSAGE BOARD|
After Galileo detected a magnetic pole on the moon, NASA sent the probe
back for another check in January. The craft's magnetometer revealed
that the pole changed direction every 5.5 hours. That's consistent
with fluctuations that would occur if Europa contained a shell of electrically conductive material, such as a salty ocean.
"The evidence that Europa's field varies temporarily, strengthens the argument that a liquid ocean exists beneath the present-day surface," Kivelson and her colleagues wrote in Science.
The eccentric magnetic pattern is associated with tidal flexing, the
powerful pull of Jupiter and neighboring moons that regularly expand
Earlier observations indicated that water ice covers Europa, a relatively
smooth satellite covered in long grooves and ridges and riddled with
what seem to be icebergs. Europa is nearly twice as large as the Earth's moon.
A false color image of cracks and ridges in the Minos Linea region of Europa
Scientists had theorized that the icy surface hid a liquid interior,
but the new study offers convincing evidence that it exists.
"The most likely explanation is that Europa has a salty, global water
ocean beneath its ice shell," said California Institute of Technology
planetary researcher David Stevenson in a Science editorial.
The question could be settled by the Europa orbiter, which NASA plans
to launch in 2003. The sophisticated satellite would use radar to
measure the depth of the icy surface and any liquid body underneath.
Given that microbial life thrives in water in even the most extreme
conditions on this planet, biologists searching for life beyond Earth
have expressed particular interest in Europa, where tidal heating could
allow liquid water near the surface.
"After Mars, (Europa is) the most attractive extraterrestrial environment within our solar system in which to seek evidence of past or present life,"
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California Institute of Technology
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