http://www.independent.co.uk/news/science/does-saturn-moon-hide-watery-caverns--and-life-1718207.html
Does Saturn moon hide watery caverns - and life?
By Ben Hirschler, Reuters
Thursday, 25 June 2009
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Ho New / Reuters
The highest resolution view ever obtained of the north polar region of Saturn's
moon Enceladus
a.. enlarge
Saturn's icy moon Enceladus could contain watery underground caverns, forming a
potential home for alien life, say scientists.
German researchers have found salt - a signature chemical for seawater - in ice
grains from vapour jets streaming out of surface cracks, providing the
strongest evidence yet of a liquid water reservoir beneath the moon's frozen
crust.
A US team said the amount of salt they had detected using a different method
suggested an earlier theory that water was boiling explosively into the vacuum
of space via geysers was wrong, and evaporation was occurring quite slowly.
One explanation for the slower evaporation may be that water is emerging from
pressurised chambers below the so-called tiger stripe fractures in the moon's
surface, said John Spencer of the Southwest Research Institute in Boulder,
Colorado.
"Our picture of its sub-surface must now be expanded to include the possibility
of misty ice caverns floored with pools and channels of salty water, lurking
beneath the tiger stripes," he wrote in a commentary on the two scientific
papers.
"What else may lurk in those salty pools, if they exist, remains to be seen."
The Cassini spacecraft first discovered huge plumes erupting from fissures near
the south pole of Enceladus in 2005, sparking speculation of a vast underground
ocean spewing vapour through giant Yellowstone-like geysers.
Since then, scientists have debated whether this meant that Enceladus
(pronounced en-SELL-ah-dus), with a diameter of only 310 miles (500 km), was
hiding a reservoir of liquid water. It is one of about 60 moons of the ringed
planet Saturn.
Frank Postberg of the Max Planck Institute for Nuclear Physics in Heidelberg
said the presence of sodium salts was compelling evidence, indicating salty
minerals were washed out from rock on Enceladus in the same way oceans absorb
salt on Earth.
He and colleagues reported they had found salty grains of ice after analysing
data from Cassini's cosmic dust detector as it flew through Saturn's outermost
ring, where Enceladus orbits.
Whether or not Enceladus harbours life remains a mystery. But the evidence of
liquid water, coupled with heat near the moon's South Pole, suggests it is
possible.
"If you have this large amount of water in contact with a rocky core and you
have heat, then you have very good conditions," Postberg said in a telephone
interview.
"On top of that we measured a slightly alkaline pH value, which is very good
for the formation of complex organic molecules."
Scientists hope to find out more when Cassini makes two more close fly-bys of
Enceladus in November.
www.nature.com/nature
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