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

[Ron Baalke]

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

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