U.S. Water News Online
WASHINGTON -- Magnetic readings of Europa, a moon of
Jupiter, strongly suggest that it has an ocean of liquid water
covered by ice, a finding that strengthens the possibility for the
presence of life, experts say.
Margaret G. Kivelson, a space physics scientist, said the evidence
from a magnetic field detection device on the Galileo spacecraft
gives the strongest evidence yet that Europa is awash with liquid
water below a thick outer layer of ice.
``This is not absolute proof that there is a salty ocean there,''
said Kivelson, a researcher at the University of California, Los
Angeles. ``The evidence is indirect. But nobody has been able to come
up with another sensible explanation.''
Kivelson is first author of a study published in the journal
Proof of liquid water on Europa ``is a good first step'' toward
finding life on the Jovian moon, she said.
``It is a long way from finding water to finding life,'' said
Kivelson, ``but it certainly makes it a more intriguing
If Europa was dry or frozen solid, she said, ``it would certainly
reduce the possibility'' of life being there.
Many experts consider Europa and Mars as the most likely places to
find life in the solar system beyond the Earth. Photos of Mars have
been interpreted as evidence that liquid water has flowed recently on
Earlier studies of Europa showed that it was covered with a thick
layer of ice. Planetary experts had suggested that there might be
liquid water beneath the ice but until now there was little evidence
to support that idea.
Kivelson and her colleagues used a magnetometer to take readings
while the Galileo spacecraft passed close to Europa last January. She
said the pattern of the moon's internal magnetic field was consistent
with the presence of an ocean on the Jovian satellite.
She said the pattern suggested a body with liquid water at least
4.5 miles deep, covered with ice that could be a half a mile to six
David Stevenson of the California Institute of Technology said in
Science that ``the most likely explanation'' for the findings
of Kivelson and her team ``is that Europa has a salty, global water
ocean beneath its ice shell.''
Kivelson said that stronger evidence for liquid water may come
from planned NASA spacecraft that will be sent to orbit around
Europa. She said a magnetometer aboard that craft could provide more
detailed evidence for water.
Jupiter has 17 named moons with four, called the Galilean
satellites, large enough to be seen by telescopes on Earth. Europa is
the brightest of the large Jovian moons.
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