Volume: 03, Issue: 15 07/27/2005 
As Cassini approached the intriguing ice world of Enceladus for its extremely close flyby on July 14, 2005, the spacecraft obtained images in several wavelengths that were used to create this false-color composite view. Image courtesy NASA/JPL.
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Most of Enceladus' larger craters appear to have softened from their original, presumably crisp appearance and are cross-cut here by numerous faults. Image courtesy NASA/JPL.
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The tortured southern polar terrain of Enceladus appears strewn with great boulders of ice in this fantastic view, one of the highest resolution images obtained so far by Cassini of any world. Image courtesy NASA/JPL.
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Discovery Launches into Orbit
Aviation Aficionados Flock to AirVenture 2005
Mars Reconnaissance Orbiter Preps for Launch
Take Part in Science Broadcasts
 

Cassini Finds Intriguing Features on Enceladus

Saturnís moon Enceladus is proving to be an intriguing target for the Cassini spacecraft. Detailed new images of the south polar region reveal distinctive geological features and the most youthful terrain seen so far on the moon. The findings point to a complex evolutionary history for Saturn's brightest, whitest satellite.

Cassini's July 14 flyby brought it within 109 miles of the icy moonís surface. 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 across in a region that is unusual in its lack of the 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. "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.

For more information or to see Cassini images on the Web, visit the following websites:
http://www.nasa.gov/cassini
http://saturn.jpl.nasa.gov
http://ciclops.org

    
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