Cassini Flies Through Watery Plumes of Saturn Moon         March 13, 2008


NASA's Cassini spacecraft performed a daring flyby of Saturn's moon
Enceladus on Wed., March 12, flying about 15 kilometers per second (32,000
mph) through icy water geyser-like jets. The spacecraft snatched up precious
samples that might point to a water ocean or organics inside the little
moon.

Scientists believe the geysers could provide evidence that liquid water is
trapped under the icy crust of Enceladus. The geysers emanate from fractures
running along the moon's south pole, spewing out water vapor at
approximately 400 meters per second (800 mph).

The new data provide a much more detailed look at the fractures that modify
the surface and will give a significantly improved comparison between the
geologic history of the moon's north pole and south pole.

New images show that compared to much of the southern hemisphere on
Enceladus--the south polar region in particular--the north polar region is
much older and pitted with craters of various sizes. These craters are
captured at different stages of disruption and alteration by tectonic
activity, and probably from past heating from below. Many of the craters
seem sliced by small parallel cracks that appear to be ubiquitous throughout
the old cratered terrains on Enceladus.

"These new images are showing us in great detail how the moon's north pole
differs from the south, an important comparison for working out the moon's
obviously complex geological history," said Carolyn Porco, Cassini imaging
team leader, Space Science Institute, Boulder, Colo. "And the success of
yesterday's daring and very low-altitude flyby means this coming summer's
very close encounter, when we get exquisitely detailed images of the surface
sources of Enceladus' south polar jets, should be an exciting 'next big
step' in understanding just how the jets are powered."

This week's flyby and another one planned for Oct. 9, 2008, were designed so
that Cassini's particle analyzers could dissect the ÒbodyÓ of the plume for
information on the density, size, composition and speed of the particles.
Among other things, scientists will use the data gathered this week to
figure out whether the gases from the plume match the gases that make up the
halo of particles around Enceladus. This may help determine how the plumes
formed.

During Cassini's closest approach, two instruments were collecting data--the
Cosmic Dust Analyzer and the Ion and Neutral Mass Spectrometer. An
unexplained software hiccup with Cassini's Cosmic Dust Analyzer instrument
prevented it from collecting any data during closest approach, although the
instrument did get data before and after the approach. During the flyby, the
instrument was switching between two versions of software programs. The new
version was designed to increase the ability to count particle hits by
several hundred hits per second. The other four fields and particles
instruments on the spacecraft, in addition to the ion and neutral mass
spectrometer, did capture all of their data, which will complement the
overall composition studies and elucidate the unique plume environment of
Enceladus.

Cassini's instruments discovered evidence for the geyser-like jets on
Enceladus in 2005, finding that the continuous eruptions of ice water create
a gigantic halo of ice dust and gas around Enceladus, which helps supply
material to Saturn's E-ring.

This was the first of four Cassini flybys of Enceladus this year. During
Wednesday's flyby, the spacecraft came within 50 kilometers (30 miles) of
the surface at closest approach, 200 kilometers (120 miles) while flying
through the plume. Future trips may bring Cassini even closer to the surface
of Enceladus. Cassini will complete its prime mission, a four-year tour of
Saturn, in June. From then on, a proposed extended mission would include
seven more Enceladus flybys. The next Enceladus flyby would take place in
August of this year.

For more images and more information, visit: http://www.nasa.gov/cassini and
http://saturn.jpl.nasa.gov .

The Cassini-Huygens mission is a cooperative project of NASA, the European
Space Agency and the Italian Space Agency. JPL, a division of the California
Institute of Technology in Pasadena, manages the Cassini-Huygens mission for
NASA's Science Mission Directorate, Washington. The Cassini orbiter was
designed, developed and assembled at JPL.

----------------------

NEWS RELEASE: 2008-044 
(Source: NASA/JPL/Space Science Institute)

Contacts:
Carolina Martinez 818-354-5011
Jet Propulsion Laboratory, Pasadena, Calif.
carolina.martinez@jpl.nasa.gov

Preston Dyches 720-974-5859
Space Science Institute, Boulder, Colo.
media@ciclops.org

-----------------------

MEDIA ADVISORY: M08-061

NASA TO RELEASE NEW DETAILS FROM CLOSE FLYBY OF SATURN MOON

WASHINGTON - NASA will hold a news conference at 2 p.m. EDT, 
Wednesday, March 26, to present new clues on the composition of the 
icy plumes jetting off the surface of Saturn's moon Enceladus. The 
findings were obtained March 12 during the closest flyby of the moon 
by the Cassini spacecraft. The briefing will take place in the NASA 
Headquarters television studio, 300 E St., S.W., Washington, and will 
be carried live on NASA Television.

Participants in the press conference will be:
- Hunter Waite, Southwest Research Institute, San Antonio, principal 
investigator, Ion and Neutral Mass Spectrometer
- John Spencer, Southwest Research Institute, Boulder, Colo., 
co-investigator, Composite Infrared Spectrometer 
- Larry Esposito, University of Colorado, Boulder, principal 
investigator, Ultraviolet Imaging Spectrograph 
- Carolyn Porco, Space Science Institute, Boulder, team leader, 
Imaging Science Subsystem 

Participating NASA centers will provide question-and-answer capability 
for reporters. 

For NASA TV streaming video, scheduling and downlink information, 
visit: 

http://www.nasa.gov/ntv