[meteorite-list] Cassini Flies Through Watery Plumes of Saturn Moon Enceladus

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri, 14 Mar 2008 15:43:50 -0700 (PDT)
Message-ID: <200803142243.PAA16849_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.cfm?release=2008-044

Cassini Flies Through Watery Plumes of Saturn Moon
Jet Propulsion Laboratory
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 "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 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.

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

Media Contact: Carolina Martinez 818-354-9382
Jet Propulsion Laboratory, Pasadena, Calif.
carolina.martinez at jpl.nasa.gov

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

2008-044
Received on Fri 14 Mar 2008 06:43:50 PM PDT