University of Arizona
UA contacts on this research:
Alfred McEwen, 520-626-4573
Elizabeth Turtle, 520-621-8284
Jason Perry, 520-626-0760
March 09, 2006
Cassini Images of Enceladus Suggest Geysers Erupt Liquid Water at the
Moon's South Pole
By Preston Dyches, CICLOPS/Space Science Institute, Boulder
Images returned from NASA's Cassini spacecraft have yielded evidence
that the geologically young south polar region of Saturn's icy moon
Enceladus may possess reservoirs of near-surface liquid water that erupt
to form geysers of the kind found in Yellowstone National Park.
This finding and others are being reported today by the Cassini Imaging
Science Team in the journal Science.
"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 Dr.
Carolyn Porco, Cassini imaging team leader at the Space Science
Institute in Boulder, Colo., and the lead author of the Science report.
"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. It doesn't get any more exciting than this."
Dr. Alfred McEwen, Dr. Elizabeth Turtle and Jason Perry of The
University of Arizona's Lunar and Planetary Laboratory are co-authors on
the article. McEwen is a member of the Cassini Imaging Science Team.
High resolution Cassini images showing the icy jets, and the towering
plume they create, reveal the abundance of the constituent particles and
the speed at which they are being ejected from Enceladus. These results
indicate that there are far too many particles being released from the
south pole of Enceladus for the source to be merely frozen mist
condensing out of a plume of water vapor, or particles that have been
blown off Enceladus by jets of water vapor arising from warm ice.
Instead, they have found a much more exciting possibility: the jets may
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.
"There are other moons in the solar system that have liquid water oceans
covered by kilometers of icy crust," said Dr. Andrew Ingersoll, an
atmospheric scientist and a co-author on the paper in Science. "What's
different here is that pockets of liquid water may be no more than ten
meters below the surface."
In the near-vacuum conditions at the moon's surface, liquid water would
boil away into space, erupting forcefully into the void and carrying
particles of ice and liquid water along with the vapor. Analysis of the
jets and plumes indicate that most of the particles eventually fall back
to the surface, giving the moon's south pole its extremely bright
veneer. Those that escape the moon's gravity go into orbit around
Saturn, forming the E ring.
Cassini images have revealed the geology of Enceladus in startling
detail, including relaxed craters and extensive surface cracks and
folds. Imaging scientists report that the moon has undergone geologic
activity over the last four and half billion years up to the present,
with the active south pole being the only place where liquid water may
currently exists near the surface. Telltale geologic features throughout
the southern hemisphere of Enceladus also point to a change in the
body's shape with time. Scientists believe these to be related to an
episode of intense heating in the moon's past that may, in turn, explain
the anomalous warmth and current activity in the south polar region.
The sources of this warmth are a major puzzle. Some combination of tidal
flexing and heating of the interior by naturally radioactive material
may provide the heat to power the geysers, which almost certainly erupt
from the narrow, warm fractures, called 'tiger stripes', seen crossing
Enceladus' south polar region. However, obtaining enough energy to
reproduce the observed heat emanating from the south pole is still a
Dr. Torrence Johnson, a satellite expert at NASA's Jet Propulsion
Laboratory, Pasadena, Calif., and a co-author, notes: "Active water
geysers on little Enceladus are a major surprise. We're still puzzled
about the details and energy sources, but what's exciting is that
Enceladus obviously figured out how to do it. Now it's up to us to
Images accompanying this release are available at
The Cassini-Huygens mission is a cooperative project of NASA, the
European Space Agency and the Italian Space Agency. The Jet Propulsion
Laboratory (JPL), a division of the California Institute of Technology
in Pasadena, manages the Cassini-Huygens mission for NASA's Science
Mission Directorate, Washington. The Cassini orbiter and its two onboard
cameras were designed, developed and assembled at JPL. The imaging team
consists of scientists from the U.S., England, France, and Germany. The
imaging operations center and team leader (Dr. C. Porco) are based at
the Space Science Institute in Boulder, Colo.
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