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.
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