Cassini provides new views of Titan's lakes and seas, celebrates 10 years since launch

The southern region images were beamed back after an Oct. 2 flyby in which a prime goal was the hunt for lakes at the south pole. A new mosaic image, created by stitching together radar images from seven Titan flybys over the last year and a half, shows a north pole pitted with giant lakes and seas, at least one of them larger than Lake Superior.
Approximately 60 percent of Titan's north polar region above 60 degrees latitude has been mapped by Cassini's radar instrument. About 14 percent of the mapped region is covered by what scientists interpret as liquid hydrocarbon lakes.

"This is our version of mapping Alaska, the northern parts of Canada, Greenland, Scandinavia and Northern Russia," said Rosaly Lopes, Cassini radar scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "It's like mapping these regions of Earth for the first time."

Lakes and seas are very common at the high northern latitudes of Titan, which is in winter now. Scientists say it rains methane and ethane there, filling the lakes and seas. These liquids also carve meandering rivers and channels on the moon's surface. Now Cassini is moving into unknown territory, the south pole of Titan. "We wanted to see if there are more lakes present there and, sure enough, there they are, three little lakes smiling back at us. Titan is indeed the land of lakes and seas," said Lopes. "It will be interesting to see the differences between the north and south polar regions."

It is now summer at Titan's south pole. A season on Titan lasts nearly 7.5 years, one quarter of a Saturn year, which is 29.5 years long. Monitoring seasonal change helps scientists understand the processes at work there.

Image Credit: NASA/JPL/USGS
High resolution image

Shown here is a portion of the image swath and an inset with details of a small portion in false color. Titan's south pole is at the bottom center. The nature and similarities between the northern and southern near-polar regions supports the idea that much of Titan's poles are climate-driven.

A few small dark patches - liquid-hydrocarbon-filled lakes - stand out, at about 70 degrees south, and are highlighted in the insert (lakes are colored blue). Other features in the scene include broad, steep-sided depressions adjoined to sinuous depressions, interpreted to be empty topographic basins or drained lakes fed by channels, and complex mottled terrain, akin to those at similar northern latitudes. Similarities in features between northern and southern hemispheres imply that the climatic conditions are also similar.

The image shown here is a 1.4-kilometer (0.87-mile) resolution, 2,250-kilometer (1,400 mile) subsection of a 4,500-kilometer (2,800-mile) long swath, which is 150 kilometers (93 miles) wide at the narrowest point. The insert is 90 by 90 kilometers (56 by 56 miles), centered at 70.5 degrees south and 113.9 degrees west. Future southern flybys will image closer to the pole and are expected to show more lakes.




Image Credit: NASA/JPL/USGS
High resolution image (10.0 MB)

This Cassini false-color mosaic shows all synthetic-aperture radar images to date of Titan's north polar region. Approximately 60 percent of Titan's north polar region, above 60 degrees north latitude, is now mapped with radar. About 14 percent of the mapped region is covered by what is interpreted as liquid hydrocarbon lakes.

Features thought to be liquid are shown in blue and black, and the areas likely to be solid surface are tinted brown. The terrain in the upper left of this mosaic is imaged at lower resolution than the remainder of the image.

Most of the many lakes and seas seen so far are contained in this image, including the largest known body of liquid on Titan. These seas are most likely filled with liquid ethane, methane and dissolved nitrogen.

Many bays, islands and presumed tributary networks are associated with the seas. The large feature in the upper right center of this image is at least 100,000 square kilometers (40,000 square miles) in area, greater in extent than Lake Superior (82,000 square kilometers or 32,000 square miles), one of Earth's largest lakes. This Titan feature covers a greater fraction of the surface, at least 0.12 percent, than the Black Sea, Earth's largest terrestrial inland sea, at 0.085 percent. Larger seas may exist, as it is probable that some of these bodies are connected, either in areas unmapped by radar or under the surface.

Of the 400 observed lakes and seas, 70 percent of their area is taken up by large "seas" greater than 26,000 square kilometers (10,000 square miles).

Scientists are making progress in understanding how the lakes may have formed. On Earth, lakes fill low spots or are created when the local topography intersects a groundwater table. Lopes and her colleagues think that the depressions containing the lakes on Titan may have formed by volcanism or by a type of erosion (called karstic) of the surface, leaving a depression where liquids can accumulate. Karstic lakes are common on Earth. For example in parts of Minnesota and central Florida there are hundreds of such lakes.

"The lakes we are observing on Titan appear to be in varying states of fullness, suggesting their involvement in a complex hydrologic system akin to Earth's water cycle. This makes Titan unique among the extra-terrestrial bodies in our solar system," said Alex Hayes, a graduate student who studies Cassini radar data at the California Institute of Technology in Pasadena.

"The lakes we have seen so far vary in size from the smallest observable, approximately 1 square kilometer (0.4 square miles), to greater than 100,000 square kilometers (40,000 square miles), which is slightly larger than the Great Lakes in the Midwestern U.S.," Hayes said. "Of the roughly 400 observed lakes, 70 percent of their area is taken up by large "seas" greater than 26,000 square kilometers (10,000 square miles)."

Future radar flybys will image closer to the southern pole and are expected to show more lakes.

Cassini mission to Saturn celebrates 10 years since launch

Celebrating the 10th anniversary of its launch from Cape Canaveral, the Cassini-Huygens mission to Saturn is once again at the center of scientific attention. Its latest discoveries about the ringed planet were a leading topic of conversation among the nearly 1,500 scientists gathered last week at a major astronomy conference in Orlando, Fla.

Cassini rode into space Oct. 15, 1997, atop a U.S. Air Force Titan IVB. Its mission: to orbit and study the Saturnian system for four years and to put the European Space Agency's Huygens Probe in position to parachute down to the frozen surface of Saturn's Earthlike moon Titan. Since entering orbit around Saturn, Cassini's scientific instruments, powered by radioisotope thermoelectric generators, have returned immense amounts of new information via NASA's global Deep Space Network to the international team of scientists working on the mission.

"With Cassini, amazing discoveries have almost become routine," says Cassini project scientist Dennis Matson of NASA's Jet Propulsion Laboratory, Pasadena, Calif., where the international mission is managed.

"Orbiting Saturn, Cassini is in the middle of the greatest natural laboratory accessible to us in space," says Matson. "With its rings, dozens of moons and magnetic environment, Saturn is like a mini-solar system, with Saturn as a stand-in for the sun, and the moons and rings like planets in formation. Through Cassini and its instruments, we are making fundamental strides in understanding the physical processes that created and govern this and other solar systems."

Some of the discoveries include ice geysers shooting from Saturn's moon Enceladus and the finding that one of Saturn's rings is created from these ice particles. Recently, scientists found that material from Enceladus is also affecting the rotation of Saturn's magnetic field. And an onboard radar instrument, which sees through clouds, has been unveiling the fascinating world of Titan, the large moon with complex chemistry and lakes of hydrocarbons.

Source: Jet Propulsion Laboratory
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