Cassini Finds Warm Cracks on Enceladus

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Image advisory: 2010-402 November 30, 2010

Cassini Finds Warm Cracks on Enceladus

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2010-402&cid=release_2010-402

PASADENA, Calif. – New images and data from NASA's Cassini spacecraft give scientists a
unique Saturn-lit view of active fissures through the south polar region of Saturn's moon
Enceladus. They reveal a more complicated web of warm fractures than previously thought.

The new images are available at: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov.

Scientists working jointly with Cassini's composite infrared spectrometer and its high-
resolution imaging camera have constructed the highest-resolution heat intensity maps yet of
the hottest part of a region of long fissures spraying water vapor and icy particles from
Enceladus. These fissures have been nicknamed "tiger stripes." Additional high-resolution
spectrometer maps of one end of the tiger stripes Alexandria Sulcus and Cairo Sulcus reveal
never-before-seen warm fractures that branch off like split ends from the main tiger stripe
trenches. They also show an intriguing warm spot isolated from other active surface fissures.

"The ends of the tiger stripes may be the places where the activity is just getting started, or is
winding down, so the complex patterns of heat we see there may give us clues to the life cycle
of tiger stripes," said John Spencer, a Cassini team scientist based at Southwest Research
Institute in Boulder, Colo.

The images and maps come from the Aug. 13, 2010, Enceladus flyby, Cassini's last remote
sensing flyby of the moon until 2015. The geometry of the many flybys between now and
2015 will not allow Cassini to do thermal scans like these, because the spacecraft will be too
close to scan the surface and will not view the south pole. This Enceladus flyby, the 11th of
Cassini's tour, also gave Cassini its last look at any part of the active south polar region in
sunlight.

The highest-resolution spectrometer scan examined the hottest part of the entire tiger stripe
system, part of the fracture called Damascus Sulcus. Scientists used the scan to measure
fracture temperatures up to190 Kelvin (minus 120 degrees Fahrenheit). This temperature
appears slightly higher than previously measured temperatures at Damascus, which were
around 170 Kelvin (minus 150 degrees Fahrenheit).

Spencer said he isn't sure if this tiger stripe is just more active than it was the last time
Cassini's spectrometer scanned it, in 2008, or if the hottest part of the tiger stripe is so narrow
that previous scans averaged its temperature out over a larger area. In any case, the new scan
had such good resolution, showing details as small as 800 meters (2,600 feet), that scientists
could see for the first time warm material flanking the central trench of Damascus, cooling off
quickly away from the trench. The Damascus thermal scan also shows large variations in heat
output within a few kilometers along the length of the fracture. This unprecedented resolution
will help scientists understand how the tiger stripes deliver heat to the surface of Enceladus.

Cassini acquired the thermal map of Damascus simultaneously with a visible-light image
where the tiger stripe is lit by sunlight reflecting off Saturn. The visible-light and thermal data
were merged to help scientists understand the relationships between physical heat processes
and surface geology.

"Our high-resolution images show that this section of Damascus Sulcus is among the most
structurally complex and tectonically dynamic of the tiger stripes," said imaging science team
associate Paul Helfenstein of Cornell University, Ithaca, N.Y. Some details in the appearance
of the landforms, such as a peculiar pattern of curving striations along the flanks of Damascus,
had not previously been noticed in ordinary sunlit images.

The day after the Enceladus flyby, Cassini swooped by the icy moon Tethys, collecting
images that helped fill in gaps in the Tethys global map. Cassini's new views of the heavily
cratered moon will help scientists understand how tectonic forces, impact cratering, and
perhaps even ancient resurfacing events have shaped the moon's appearance.

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. The composite infrared spectrometer team is based at NASA's
Goddard Space Flight Center, Greenbelt, Md., where the instrument was built.

More details are also available at the imaging team's website http://ciclops.org and the
composite infrared spectrometer team's website http://cirs.gsfc.nasa.gov .

Additional contact: Joe Mason, Space Science Institute, Boulder, Colo.
720-974-5859 or jmason@ciclops.org .

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