Cassini Spacecraft Finds Ocean May Exist Beneath Titan's Crust
PASADENA, Calif. - NASA's Cassini spacecraft has discovered evidence that
points to the existence of an underground ocean of water and ammonia on
Saturn's moon Titan. The findings, made using radar measurements of Titan's
rotation, will appear in the March 21 issue of the journal Science.
"With its organic dunes, lakes, channels and mountains, Titan has one of
the most varied, active and Earth-like surfaces in the solar system," said
Ralph Lorenz, lead author of the paper and Cassini radar scientist at the
Johns Hopkins Applied Physics Laboratory in Laurel, Md., "Now we see changes
in the way Titan rotates, giving us a window into Titan's interior beneath the surface."
Members of the mission's science team used Cassini's Synthetic Aperture Radar
to collect imaging data during 19 separate passes over Titan between October 2005
and May 2007. The radar can see through Titan's dense, methane-rich atmospheric
haze, detailing never-before-seen surface features and establishing their locations
on the moon's surface.
Using data from the radar's early observations, the scientists and radar engineers
established the locations of 50 unique landmarks on Titan's surface. They then
searched for these same lakes, canyons and mountains in the reams of data returned
by Cassini in its later flybys of Titan. They found prominent surface features had
shifted from their expected positions by up to 30 kilometers (19 miles). A systematic
displacement of surface features would be difficult to explain unless the moon's icy
crust was decoupled from its core by an internal ocean, making it easier for the crust to move.
"We believe that about 100 kilometers (62 miles) beneath the ice and organic-rich
surface is an internal ocean of liquid water mixed with ammonia," said Bryan Stiles
of NASA's Jet Propulsion Laboratory in Pasadena, Calif. Stiles is a contributing author
to the paper.
The study of Titan is a major goal of the Cassini-Huygens mission because it
may preserve, in deep-freeze, many of the chemical compounds that preceded life on Earth.
Titan is the only moon in the solar system that possesses a dense atmosphere. The moon's
atmosphere is 1.5 times denser than Earth's. Titan is the largest of Saturn's moons,
bigger than the planet Mercury.
"The combination of an organic-rich environment and liquid water is very appealing to
astrobiologists," Lorenz said. "Further study of Titan's rotation will let us understand
the watery interior better, and because the spin of the crust and the winds in the atmosphere
are linked, we might see seasonal variation in the spin in the next few years."
Cassini scientists will not have long to wait before another go at Titan. On March 25, just
prior to its closest approach at an altitude of 1,000 kilometers (620 miles), Cassini will
employ its Ion and Neutral Mass Spectrometer to examine Titan's upper atmosphere. Immediately
after closest approach, the spacecraft's Visual and Infrared Mapping Spectrometer will
capture high-resolution images of Titan's southeast quadrant.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and
the Italian Space Agency. The mission is managed by JPL, a division of the California
Institute of Technology in Pasadena. The Cassini orbiter also was designed, developed and
assembled at JPL. The radar instrument was built by JPL and the Italian Space Agency,
working with team members from the United States and several European countries.
For information about Cassini visit: http://www.nasa.gov/cassini
Media contacts: DC Agle/Carolina Martinez 818-393-9011/818-354-9382
Jet Propulsion Laboratory, Pasadena, Calif.
Dwayne Brown 202-358-2726
NASA Headquarters, Washington