[meteorite-list] Cassini Finds Recent and Unusual Geology on Enceladus

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue Jul 26 11:57:47 2005
Message-ID: <200507261556.j6QFutr12490_at_zagami.jpl.nasa.gov>

Erica Hupp/Dolores Beasley
Headquarters, Washington July 26, 2005
(Phone: 202/358-1237/1753)

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

Preston Dyches
Space Science Institute, Boulder, Colo.
(Phone: 720/974-5859)

RELEASE: 05-201

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 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 tectonic patterns unique to Enceladus.
These features set the region apart from the rest 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 southern most 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 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 satellite, 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.
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
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 (JPL), a division of the California
Institute of Technology in Pasadena, manages the mission for
NASA's Science Mission Directorate. 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

http://ciclops.org

-end-
Received on Tue 26 Jul 2005 11:56:54 AM PDT