[meteorite-list] Saturn's Moons Titan and Enceladus Seen by Cassini

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri Feb 18 21:43:14 2005
Message-ID: <200502190242.j1J2gvK24681_at_zagami.jpl.nasa.gov>

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov

Carolina Martinez (818) 354-9382
Jet Propulsion Laboratory, Pasadena, Calif.

Press Release: 2005-030 February 18, 2005

Saturn's Moons Titan and Enceladus Seen by Cassini

NASA's Cassini spacecraft has had a busy week, snapping stunning
new images of two of Saturn's moons -- smoggy Titan on Feb. 15
and wrinkled Enceladus on Feb. 16.

Visible in radar images released today are a crater, channels,
and terrain similar to the area where the European Space Agency's
Huygens probe landed on Jan. 14.

The crater is approximately 60 kilometers (37 miles) in diameter.
Earlier this week, the radar team released an image of a giant
impact crater dubbed "Circus Maximus," about 440 kilometers wide
(273 miles).

"The appearance of the small crater and the extremely bright,
hence rough, blanket of material surrounding it is indicative of
an origin by impact," said Dr. Jonathan Lunine, Cassini
interdisciplinary scientist from the University of Arizona,
Tucson.

>From the crater's size, scientists estimate that it was created
when a comet or asteroid roughly 5 to 10 kilometers (3 to 6
miles) in size slammed into the surface of Titan. The feature
lacks a central peak, suggesting that it has been eroded or
otherwise modified since formation. Rainfall, wind erosion, and
softening of the solid material in which the crater formed are
all possible processes that might have altered this impact
feature.

Also visible in the radar images are channels located just east of
Circus Maximus, the large impact crater. The longest channel is
approximately 200 kilometers long (124 miles). The channels
appear to flow from the slopes of the crater. The fluid was most
likely liquid methane, given the extremely cold ambient conditions
at the surface of Titan. The area somewhat resembles the rubble-
strewn plains in the region where the Huygens probe landed.

Just one day after the Titan flyby, Cassini turned its sights on
Saturn's moon Enceladus, revealing a fascinating, tortured world
of ice. The spacecraft swept within 1,180 kilometers (730 miles)
of the moon's wrinkled surface, providing the first-ever high
resolution images of this world with the brightest, most
reflective surface in the solar system.

Since NASA's Voyager spacecraft flew past Enceladus in 1980 and
1981, planetary scientists have been intrigued by the moon's
wrinkled terrain and smooth plains, some of which appeared to be
relatively free of impact craters. Smooth, crater-free surfaces
on moons and planets indicate geologically young ages, while
wrinkles may indicate tectonic activity or volcanism.

"Cassini has now viewed these terrains at almost 10 times better
resolution than Voyager," said Dr. Carolyn Porco, Cassini imaging
team leader based at the Space Science Institute in Boulder,
Colo. "Interestingly, the icy surface of Enceladus appears to
have similarities to both Europa and Ganymede -- two prominent
icy satellites of Jupiter -- and topographic relief of about 1
kilometer [.6 mile]. Both Europa and Ganymede are thought to have
subsurface water layers, or 'oceans,' so the similarities with
Enceladus are intriguing."

One view released today is a high-resolution mosaic showing
complex systems of fractures and resurfaced terrain. Among the
most intriguing features in the images are a series of small,
dark spots, which in many places seem to be aligned in chains
parallel to narrow fractures.

A false-color view shows some linear features on Enceladus with a
slightly different color from their surroundings. Different
colors of ice may be caused by varying compositions or varying
ice crystal sizes. Either one can indicate different formation
mechanisms or different ages. Another early highlight from the
flyby is a high-resolution stereo view of Enceladus. Stereo views
are helpful in interpreting the moon's complex topography.

Other preliminary results from the visual and infrared mapping
spectrometer show a surface composed of only pure water ice, with
no other compounds detected. Ammonia or ammonium compounds and
carbon dioxide were expected, but not seen in the data. Further
analysis may find trace amounts. "The spectra look like
laboratory fabricated water ice, indicating the ice is quite
pure," said Dr. Roger N. Clark, Cassini science team member at
the U.S. Geological Survey in Denver.

During the latest flybys, Cassini was 1,577 kilometers (980
miles) above Titan, and 1,180 kilometers (730 miles) above
Enceladus. Cassini will conduct an even closer flyby of
Enceladus on March 9, coming within approximately 500 kilometers
(310 miles) of its surface. More than 40 additional Titan flybys
are planned.

The pictures are available at http://saturn.jpl.nasa.gov,
http://www.nasa.gov/cassini and http://ciclops.org.

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 Cassini-Huygens mission for
NASA's Science Mission Directorate, Washington, D.C. The Cassini
orbiter and its two onboard cameras were designed, developed and
assembled at JPL. The imaging team is based at the Space Science
Institute, Boulder, Colo.
                              -end-
Received on Fri 18 Feb 2005 09:42:57 PM PST