News Release: 2007-026 March 13, 2007
Cassini Spacecraft Images Seas on Saturn's Moon Titan
Instruments on NASA's Cassini spacecraft have found evidence for seas,
likely filled
with liquid methane or ethane, in the high northern latitudes of
Saturn's moon Titan. One
such feature is larger than any of the Great Lakes of North America and
is about the same
size as several seas on Earth.
Cassini's radar instrument imaged several very dark features near
Titan's north pole.
Much larger than similar features seen before on Titan, the largest
dark feature measures
at least 100,000 square kilometers (39,000 square miles). Since the
radar has caught only
a portion of each of these features, only their minimum size is known.
Titan is the second
largest moon in the solar system and is about 50 percent larger than
Earth's moon.
"We've long hypothesized about oceans on Titan and now with multiple
instruments we
have a first indication of seas that dwarf the lakes seen previously,"
said Dr. Jonathan
Lunine, Cassini interdisciplinary scientist at the University of
Arizona, Tucson.
While there is no definitive proof yet that these seas contain liquid,
their shape, their dark
appearance in radar that indicates smoothness, and their other
properties point to the
presence of liquids. The liquids are probably a combination of methane
and ethane, given
the conditions on Titan and the abundance of methane and ethane gases
and clouds in
Titan's atmosphere.
Cassini's visual and infrared mapping spectrometer also captured a view
of the region,
and the team is working to determine the composition of the material
contained within
these features to test the hypothesis that they are liquid-filled.
The imaging cameras, which provide a global view of Titan, have imaged
a much larger,
irregular dark feature. The northern end of their image corresponds to
one of the radar-
imaged seas. The dark area stretches for more than 1,000 kilometers
(620 miles) in the
image, down to 55 degrees north latitude. If the entire dark area is
liquid-filled, it would
be only slightly smaller than Earth's Caspian Sea. The radar data show
details at the
northern end of the dark feature similar to those seen in earlier radar
observations of
much smaller, liquid-filled lakes. However, to determine if the entire
dark feature is a
liquid-filled basin will require investigation through additional radar
flyovers later in the
mission.
The presence of these seas reinforces current thinking that Titan's
surface must be re-
supplying methane to its atmosphere, the original motivation almost a
quarter century ago
for the theoretical speculation of a global ocean on Titan.
Cassini's instruments are peeling back the haze that shrouds Titan,
showing high northern
latitudes dotted with seas hundreds of miles across, and hundreds of
smaller lakes that
vary from several to tens of miles.
Due to the new discoveries, team members are re-pointing Cassini's
radar instrument
during a May flyby so it can pass directly over the dark areas imaged
by the cameras.
For images and more information visit:
www.nasa.gov/cassini
and
saturn.jpl.nasa.gov
.
Deirdre Kelleghan
  