Almost all of hydrocarbon seas and lakes on the surface of Saturn's moon Titan cluster around the north pole, as can be seen in this mosaic from NASA's Cassini mission. This mosaic, made from near-infrared images of Titan obtained by Cassini's imaging science subsystem, shows a view from the north pole (upper middle of mosaic) down to near the equator at the bottom . Here, the seas and lakes appear as dark shapes, embedded in some kind of bright terrain. Titan is the only world in the solar system other than Earth that is known to have stable bodies of liquid on the surface. Titan's, however, are composed of liquid ethane and methane rather than liquid water.
The bright area suggests the surface material around the lakes is unique and might explain why almost all of Titan's lakes are found in this region. It appears to cover much of the surface north of 65 to 70 degrees north latitude on this side of Titan. Titan's lakes have very distinctive shapes -- rounded cookie-cutter silhouettes and steep sides - and a variety of formation mechanisms have been proposed. The explanations range from the collapse of land after a volcanic eruption to karst terrain, where liquids dissolve soluble bedrock. Karst terrains on Earth can create spectacular topography such as the Carlsbad Caverns in New Mexico.
The north pole is in the upper middle in this view. The largest of the dark shapes, at the upper right, is Kraken Mare, which is about the size of the Caspian Sea and Lake Superior put together. To its left lies Ligeia Mare, the second largest sea which measures about 300 miles (500 kilometers) across. And below them is Punga Mare, which lies near the north pole and is about 240 miles (380 kilometers) across.
The surface around the lakes appears brighter than Titan's generally bland (darker grey) mid-latitudes. At the bottom of the mosaic, Titan's largest impact structure, Menrva (earlier ISS views: PIA06154 or PIA08365; RADAR view: PIA14541), can be seen as a bright feature almost completed surrounded by darker areas of widespread dunes. In this view, features at low latitudes are harder to discern because they were close to the horizon when these high-latitude observations were made.
The near-infrared images that make up this mosaic were obtained by Cassini's imaging science subsystem on July 26, 2013. They were obtained in the near infrared band of light (938 nanometers), close to the visible range of light that human eyes can see. To human eyes, the lakes would still appear darker than the surrounding terrain. Seven imaging footprints, involving four images each, were used to make this mosaic in order to maximize signal from Titan's surface through the hazy atmosphere. Image scale is 1.78 miles (2.86 kilometers) per pixel.
Until now, Cassini's imaging science subsystem has only been able to capture distant, oblique or partial views of this area (e.g., PIA08930 and PIA12812 ). Three recent flybys provided better viewing geometry now that sunlight has pierced the winter darkness that shrouded Titan's north pole at Cassini's arrival in the Saturn system nine years ago. A thick cap of haze that once hung over the north pole has also dissipated as northern summer approaches. And, thankfully, Titan's beautiful, almost cloudless, rain-free weather continued during Cassini's flybys this past summer.
For comparison, Cassini's visual and infrared spectrometer also obtained data on the same area around the same time: PIA17470. Other imaging camera views can be seen at PIA17471 and PIA17473.
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 Cassini-Huygens mission for NASA\'s Science Mission Directorate, Washington, D.C. The imaging team consists of scientists from the US, England, France, and Germany. The visual and infrared mapping spectrometer team is based at the University of Arizona. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.