Cassini Pinpoints Source of Jets on Saturn's Moon Enceladus

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
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http://www.jpl.nasa.gov

Carolina Martinez 818-354-9382
Jet Propulsion Laboratory, Pasadena, Calif.
carolina.martinez@jpl.nasa.gov

Preston Dyches 720-974-5859
Space Science Institute, Boulder, Colo.
media@ciclops.org

News Release: 2008-160 Aug. 14, 2008

Cassini Pinpoints Source of Jets on Saturn's Moon Enceladus

PASADENA, Calif. -- In a feat of interplanetary sharpshooting, NASA's Cassini spacecraft
has pinpointed precisely where the icy jets erupt from the surface of Saturn's geologically
active moon Enceladus.

New carefully targeted pictures reveal exquisite details in the prominent south polar "tiger
stripe" fractures from which the jets emanate. The images show the fractures are about 300
meters (980 feet) deep, with V-shaped inner walls. The outer flanks of some of the fractures
show extensive deposits of fine material. Finely fractured terrain littered with blocks of ice
tens of meters in size and larger (the size of small houses) surround the fractures.

"This is the mother lode for us," said Carolyn Porco, Cassini imaging team leader at the
Space Science Institute, Boulder, Colo. "A place that may ultimately reveal just exactly what
kind of environment -- habitable or not -- we have within this tortured little moon."

One highly anticipated result of this flyby was finding the location within the fractures from
which the jets blast icy particles, water vapor and trace organics into space. Scientists are
now studying the nature and intensity of this process on Enceladus, and its effects on
surrounding terrain. This information, coupled with observations by Cassini's other
instruments, may answer the question of whether reservoirs of liquid water exist beneath the
surface.

The high-resolution images were acquired during an Aug. 11, 2008, flyby of Enceladus, as
Cassini sped past the icy moon at 64,000 kilometers per hour (40,000 miles per hour). A
special technique, dubbed "skeet shooting" by the imaging team, was developed to cancel
out the high speed of the moon relative to Cassini and obtain the ultra-sharp views.
"Knowing exactly where to point, at just the right time, was critical to this event," said Paul
Helfenstein, Cassini imaging team associate at Cornell University, Ithaca, NY., who
developed and used the skeet-shoot technique to design the image sequence. "The
challenge is equivalent to trying to capture a sharp, unsmeared picture of a distant roadside
billboard with a telephoto lens out the window of a speeding car."

Helfenstein said that from Cassini's point of view, "Enceladus was streaking across the sky
so quickly that the spacecraft had no hope of tracking any feature on its surface. Our best
option was to point the spacecraft far ahead of Enceladus, spin the spacecraft and camera
as fast as possible in the direction of Enceladus' predicted path, and let Enceladus overtake
us at a time when we could match its motion across the sky, snapping images along the
way."

For scientists, having the combination of high-resolution snapshots and broader images
showing the whole region is critical for understanding what may be powering the activity on
Enceladus.

"There appears to have been extensive fallout of icy particles to the ground, along some of
the fractures, even in areas that lie between two jet source locations, though any immediate
effects of presently active jets are subtle," said Porco.

Imaging scientists suggest that once warm vapor rises from underground to the cold surface
through narrow channels, the icy particles may condense and seal off an active vent. New
jets may then appear elsewhere along the same fracture.

"For the first time, we are beginning to understand how freshly erupted surface deposits
differ from older deposits," said Helfenstein, an icy moons expert. "Over geologic time, the
eruptions have clearly moved up and down the lengths of the tiger stripes."

The new images, with jet source locations labeled, are available at:
http://www.nasa.gov/cassini, http://saturn.jpl.nasa.gov and http://ciclops.org .

The Cassini-Huygens mission is a cooperative project of NASA, the European Space
Agency and the Italian Space Agency. The Jet Propulsion Laboratory, 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 is based at
the Space Science Institute, Boulder, Colo.

-end-

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