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March 9, 2006: NASA's Cassini spacecraft may have
found evidence of liquid water reservoirs that erupt in Yellowstone-like
geysers on Saturn's moon Enceladus. The rare occurrence of
liquid water so near the surface raises many new questions
about this mysterious moon.
 "We
realize that this is a radical conclusion -- that we may have
evidence for liquid water within a body so small and so cold,"
said Carolyn Porco, Cassini imaging team leader at the Space
Science Institute, Boulder, Colo. "However, if we are
right, we have significantly broadened the diversity of solar
system environments where we might possibly have conditions
suitable for living organisms."
Right:
Icy fountains shoot out of Saturn's moon Enceladus. [More]
High-resolution
Cassini images show icy jets and towering plumes ejecting
huge quantities of particles at high speed. Scientists examined
several models to explain the process. They ruled out the
idea the particles are produced or blown off the moon's surface
by vapor created when warm water ice converts to a gas. Instead,
scientists have found evidence for a much more exciting possibility.
The jets might be erupting from near-surface pockets of liquid
water above 0 degrees Celsius (32 degrees Fahrenheit), like
cold versions of the Old Faithful geyser in Yellowstone: illustration.
"We
previously knew of at most three places where active volcanism
exists: Jupiter's moon Io, Earth, and possibly Neptune's moon
Triton. Cassini changed all that, making Enceladus the latest
member of this very exclusive club, and one of the most exciting
places in the solar system," said John Spencer, Cassini
scientist, Southwest Research Institute, Boulder.
"Other
moons in the solar system [may] have liquid-water oceans covered
by kilometers of icy crust," said Andrew Ingersoll, imaging
team member and atmospheric scientist at the California Institute
of Technology, Pasadena, Calif. "What's different here
is that pockets of liquid water may be no more than tens of
meters below the surface."
"As
Cassini approached Saturn, we discovered the Saturnian system
is filled with oxygen atoms. At the time we had no idea where
the oxygen was coming from," said Candy Hansen, Cassini
scientist at NASA's Jet Propulsion Laboratory (JPL) in Pasadena.
"Now we know Enceladus is spewing out water molecules,
which break down into oxygen and hydrogen."
Below:
A Cassini image of Encaladus. The blue-green "tiger stripes"
are thought to be the source of Enceladus's water jets. [More]
Above:
Cassini's infrared spectrometer took the temperature of a
tiger stripe. The fissure is at least 15 degrees K warmer
than its surroundings--a sign of geothermal activity. [More]
Scientists
still have many questions. Why is Enceladus so active? Might
this activity have been continuous enough over the moon's
history for life to have had a chance to take hold in the
moon's interior? In the spring of 2008, scientists will get
another chance to look at the geysers--and another crack at
answering these questions--when Cassini flies within 350 kilometers
(approximately 220 miles) of Enceladus.
"There's
no question, along with the moon Titan, Enceladus should be
a very high priority for us," said Jonathan Lunine, Cassini
interdisciplinary scientist, University of Arizona, Tucson,
Ariz. "Saturn has given us two exciting worlds to explore."
Mission
scientists report these and other Enceladus findings in this
week's issue of Science.
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Source: NASA Press Release | Production Editor:
Dr. Tony Phillips | Credit: Science@NASA
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