[meteorite-list] Cassini Images of Enceladus Suggest Geysers Erupt Liquid Water at the Moon's South Pole

[Ron Baalke]

University Communications
University of Arizona
Tucson, 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 
problem.

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 crack 
the mystery."

Images accompanying this release are available at
     http://ciclops.org
     http://saturn.jpl.nasa.gov
and
     http://www.nasa.gov/cassini

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.

Related Web sites:

* http://ciclops.org
* http://saturn.jpl.nasa.gov
* http://www.nasa.gov/cassini
* http://www.lpl.arizona.edu