Before and After images show first direct evidence of changing
weather on Saturn's moon
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 over Titan.
In images obtained less than two months ago (below), the Titan
skies were cloud free, except for a patch of clouds observed over
the moon's south pole. In images taken Monday, December 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
(CA).
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.
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
(CO).
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
(CO). "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.
(Photos Courtesy of Credit: NASA/JPL/Space Science
Institute)