Cassini Shows Before and After Look at Saturn's Moon Titan
Cassini's second close flyby of Titan completes a 'before'
and 'after' look at the fuzzy moon and provides the first
direct evidence of changing weather patterns in the skies
Image right: Cassini has found Titan's upper atmosphere to consist of a surprising number of layers of haze, as shown in this ultraviolet image of Titan's night side limb, colorized to look like true color.Click for full image/caption.
In images obtained less than two months ago, the Titan skies
were cloud free, except for a patch of clouds observed over
the moon's south pole. In images taken Monday, Dec. 13,
during Cassini's second close flyby of Titan, several
extensive patches of clouds have formed.
"We see for the first time discrete cloud features at mid-
latitudes, which means we see direct evidence of weather,
and we can get wind speeds and atmospheric circulation over
a region we hadn't been able to measure before," said Dr.
Kevin Baines, Cassini science-team member with the visual
and infrared mapping spectrometer, from NASA's Jet
Propulsion Laboratory, Pasadena, Calif.
The latest data and other results from Cassini's close
observations of Saturn's moons Titan and Dione were
presented today at a news conference during the American
Geophysical Union fall meeting in San Francisco.
Cassini swept within 1,200 kilometers (750 miles) of Titan's
surface on Monday, and took a close look at the icy moon
Dione just one day later. During the flyby, Cassini
captured a stunning view of Titan's night side with the
atmosphere shimmering in its own glow. This allows
scientists to study the detached haze layers, which extend
some 400 kilometers (249 miles) above Titan.
Image left: Cassini captured Dione against the globe of Saturn as it approached the icy moon for its close rendezvous on Dec. 14, 2004. Click for full image/caption.
Images from Cassini's cameras show regions on Titan that had
not been seen clearly before, as well as fine details in
Titan's intermittent clouds. The surface features may be
impact related, but without information on their height, it
is too soon to know for sure. No definitive craters have
been seen in these images, though several bright rings or
circular features are seen in dark terrain.
Cassini imaging scientists are intrigued by the complex
braided structure of surface fractures on Dione. To the
surprise of scientists, the wispy terrain features do not
consist of thick ice deposits, but bright ice cliffs created
by tectonic features. "This is one of the most surprising
results so far. It just wasn't what we expected," said Dr.
Carolyn Porco, Cassini imaging team leader, Space Science
Institute, Boulder, Colo.
Other Cassini results presented at the meeting included
observations made by the ultraviolet imaging spectrograph
instrument, which indicates that the nearby environment of
the rings and moons in the Saturn system is filled with ice,
and atoms derived from water. Cassini researchers are
seeing large changes in the amount of oxygen atoms in the
Saturn system. A possible explanation for the fluctuation
in oxygen is that small, unseen icy moons have been
colliding with Saturn's E ring," said Dr. Larry Esposito,
principal investigator of the imaging spectrograph
instrument, University of Colorado, Boulder, Colo. "These
collisions may have produced small grains of ice, which
yielded oxygen atoms." Esposito presented these findings at
the meeting, and a paper on the subject appears in the
online version of the journal Science.
According to Esposito, Saturn's ring particles may have
formed originally from pure ice. But they have since been
subjected to continual bombardment by meteorites, which has
contaminated the ice and caused the rings to darken. Over
time, continuous meteorite bombardment has likely spread the
dirty material resulting from the collisions over a wide
area in the rings. "The evidence indicates that in the last
10 to 100 million years, fresh material probably was added
to the ring system," said Esposito. These renewal events
are from fragments of small moons, each probably about 20
kilometers (12 miles) across.
Images and more information about the Cassini mission are
available at 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 mission for
NASA's Science Mission Directorate, Washington, D.C. JPL
designed, developed and assembled the Cassini orbiter. The
European Space Agency built and managed the development of
the Huygens probe and is in charge of the probe operations.
The Italian Space Agency provided the high-gain antenna,
much of the radio system and elements of several of
Cassini's science instruments.
Carolina Martinez (818) 354-9382
NASA's Jet Propulsion Laboratory