Carolina Martinez (818) 354-9382
Jet Propulsion Laboratory, Pasadena, Calif.

Erica Hupp/Dolores Beasley (202/358-1237/1753)
NASA Headquarters, Washington

Preston Dyches (720) 974-5859
Cassini Imaging Central Laboratory for Operations
Space Science Institute, Boulder, Colo.

News Release: 2005-121 July 26, 2005

Cassini Finds Recent and Unusual Geology on Enceladus

NASA's Cassini spacecraft has obtained new, detailed images of the south polar region of
Saturn's moon Enceladus. The data reveal distinctive geological features and the most youthful
terrain seen on the moon. These findings point to a very complex evolutionary history for
Saturn's brightest, whitest satellite.

Cassini's July 14 flyby brought it within 175 kilometers (109 miles) of the surface of the icy
moon. The close encounter revealed a landscape near the south pole almost entirely free of
impact craters. The area is also littered with house-sized ice boulders carved by unique tectonic
patterns found only in this region of the moon.

As white as fresh snow, Enceladus has the most reflective surface in the solar system. Previous
Cassini flybys revealed Enceladus, in contrast to Saturn's other icy moons, has lightly cratered
regions, fractured plains and wrinkled terrain.

The new findings add to the story of a body that has undergone multiple episodes of geologic
activity spanning a considerable portion of its lifetime. The moon's southernmost latitudes have
likely seen the most recent activity.

These same latitudes may also bear the scars of a shift in the moon's spin rate. If true, this
speculation may help scientists understand why Enceladus has a tortured-looking surface, with
pervasive crisscrossing faults, folds and ridges. The most remarkable images show ice blocks
about 10 to 100 meters (33 to 328 feet) across in a region that is unusual in its lack of the very
fine-grained frost that seems to cover the rest of Enceladus.

"A landscape littered with building-sized blocks was not expected," said Dr. Peter Thomas, an
imaging-team member from Cornell University, Ithaca, N.Y. "The minimal cover of finer
material and the preservation of small, crossing fracture patterns in the surrounding areas
indicate that this region is young compared to the rest of Enceladus."

False color composites of this region, created from the most recent images, show the largest
exposures of coarse-grained ice fractures seen anywhere on the moon, which also supports the
notion of a young surface at southern latitudes. Some of the latest images may hint at the answer.
The images revealed additional examples of a distinctive "Y-shaped" tectonic feature on
Enceladus. In this unusual element, parallel ridges and valleys appear to systematically fold and
deform around the south polar terrains.

"These tectonic features define a boundary that isolates the young, south polar terrains from
older terrains on Enceladus," noted Dr. Paul Helfenstein, an associate of the imaging team also at
Cornell University. "Their placement and orientation may tell us a very interesting story about
the way the rotation of Enceladus has evolved over time and what might have provided the
energy to power the geologic activity that has wracked this moon."

The apparent absence of sizable impact craters also suggests the south pole is younger than other
terrain on Enceladus. All these indications of youth are of great interest to scientists, who have
long suspected Enceladus as one possible source of material for Saturn's extensive and diffuse E
ring, which coincides with the moon's orbit. Young terrain requires a means to generate the heat
needed to modify the surface. Other Cassini instrument teams are working to understand data
about the temperature, composition, particles and magnetic field. Together with image
interpretation, these data can create a more complete picture.

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 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 operations center is based at the Space Science
Institute in Boulder, Colo.

These Cassini images are available on the Web at: http://www.nasa.gov/cassini ,
http://saturn.jpl.nasa.gov and http://ciclops.org .