The Cassini spacecraft, using its radar system, has discovered very strong
evidence for hydrocarbon lakes on Titan. Dark patches, which resemble
terrestrial lakes, seem to be sprinkled all over the high latitudes
surrounding Titan's north pole.
Scientists have speculated that liquid methane or ethane might form lakes
on Titan, particularly near the somewhat colder polar regions. In the
images, a variety of dark patches, some with channels leading in or out
of them, appear. The channels have a shape that strongly implies they were
carved by liquid. Some of the dark patches and connecting channels are
completely black, that is, they reflect back essentially no radar signal,
and hence must be extremely smooth. In some cases rims can be seen around
the dark patches, suggesting deposits that might form as liquid
evaporates. The abundant methane in Titan's atmosphere is stable as a
liquid under Titan conditions, as is its abundant chemical product,
ethane, but liquid water is not. For all these reasons, scientists
interpret the dark areas as lakes of liquid methane or ethane, making
Titan the only body in the solar system besides Earth known to possess
lakes. Because such lakes may wax and wane over time, and winds may alter
the roughness of their surfaces, repeat coverage of these areas should
test whether these are indeed bodies of liquid.
These two radar images were acquired by the Cassini radar instrument in
synthetic aperture mode on July 21, 2006. The top image centered near 80
degrees north, 92 degrees west measures about 420 kilometers by 150
kilometers (260 miles by 93 miles). The lower image centered near 78
degrees north, 18 degrees west measures about 475 kilometers by 150
kilometers (295 miles by 93 miles). Smallest details in this image are
about 500 meters (1,640 feet) across.
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 mission for NASA's Science Mission Directorate,
Washington, D.C. The Cassini orbiter 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 more information about the Cassini-Huygens mission visit
http://saturn.jpl.nasa.gov/home/index.cfm.
