Jupiter moon may have a saltwater ocean
SAN FRANCISCO, California
(Reuters) -- Scientists studying data
sent back to Earth from NASA's
Galileo spacecraft have concluded that
Jupiter's largest moon, Ganymede, may
possess a huge salt-water ocean
beneath its crusty surface.
Galileo probe data on two other Jovian
moons -- Europa and Callisto -- has already indicated that they probably have
subsurface water, a key building block for life.
Now, Ganymede -- which is larger than Mercury or Pluto -- also looks likely
be concealing a thick layer of melted, salty water beneath its icy crust,
researchers told a meeting of the American Geophysical Union here Saturday.
Margaret Kivelson of the University of
California-Los Angeles said that magnetic
readings taken by the Galileo craft during close
approaches in May 2000 and earlier were "highly
suggestive" that a salty, liquid ocean existed there.
"It would need to be something more electrically
conductive than solid ice," she said, adding that a
melted layer of water several kilometers or miles thick, beginning within 120
miles of Ganymede's surface would fit the data if it were about as salty as
Other scientists studying readings from an infrared spectrometer to identify
surface materials on Ganymede said portions of the moon appear to have types
of salt minerals that would have been left behind by exposure of salty water
near or on the surface.
"They are similar to the hydrated salt minerals we see on Europa, possibly
result of brine making its way to the surface by eruptions or through cracks,"
said Thomas McCord, a geophysicist at the University of Hawaii, Honolulu.
That hypothesis is also bolstered by new, high-resolution images of Ganymede
sent back by Galileo, which hint that water or slushy ice may have surfaced
through the fractured crust to create smooth areas in between separated areas
Dr. Dave Stevenson of the California Institute of Technology said natural
radioactivity in Ganymede's rocky interior should provide enough heating to
maintain a stable layer of liquid water between two layers of ice, about 90 to
120 miles below the surface.
"I would have been surprised if Ganymede had not had an ocean, but the
of whether it's there is different than the issue of whether you can expect to see
it clearly in the data," Stevenson said.
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