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http://www.jpl.nasa.gov
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
NEWS RELEASE: 2008-044 March 13, 2008
Cassini Flies Through Watery Plumes of Saturn Moon
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 "body" 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
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.
-end-
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