To the bottom of Titan's deep sea
Sen—The Cassini spacecraft has been gathering information on the lakes and seas of Titan, Saturn's largest moon and the only other world in the Solar System known to have liquid on its surface.
Titan is unique because it has a dense atmosphere and many Earth like characteristics including seas, lagoons, rivers, mountains and rain. However, the liquid that forms the cycle of precipitation and evaporation is not water, but hydrocarbons such as methane and ethane.
Nearly all of the lakes and seas are located in the northern hemisphere in area about 600 miles (900 km) by 1,100 miles (1,800 km).
The close flybys of Titan have enabled Cassini to piece together the most detailed image map of the region to date. The mosaic shows nearly all the seas and most of the lakes, including Titan's largest sea, Kraken Mare, and its second largest sea called Ligeia Mare.
The study of Titan's seas included measuring the depth of Ligeia Mare, the first time scientists have been able to measure the depth of surface liquid. The liquid in this sea is very pure with a surface "as smooth as the paint on our cars" according to a NASA statement, allowing Cassini's radar signal to pass through it easily to discover the sea is about 560 feet (170 metres) deep.
"Ligeia Mare turned out to be just the right depth for radar to detect a signal back from the sea floor, which is a signal we didn't think we'd be able to get," said Marco Mastrogiuseppe, a Cassini radar team associate at Sapienza University of Rome. "The measurement we made shows Ligeia to be deeper in at least one place than the average depth of Lake Michigan."
Steve Wall, the radar team lead at NASA's Jet Propulsion Laboratory (JPL) explained the significance of the research on Titan. "Learning about surface features like lakes and seas helps us to understand how Titan's liquids, solids and gases interact to make it so Earth-like. While these two worlds aren't exactly the same, it shows us more and more Earth-like processes as we get new views."
Randolph Kirk, a Cassini radar team member at the U.S. Geological Survey said: "Scientists have been wondering why Titan's lakes are where they are. These images show us that the bedrock and geology must be creating a particularly inviting environment for lakes in this box. We think it may be something like the formation of the prehistoric lake called Lake Lahontan near Lake Tahoe in Nevada and California, where deformation of the crust created fissures that could be filled up with liquid."
The data captured by Cassini on its lakes and seas has enabled scientists for the first time to estimate the total volume of liquid hydrocarbon on Titan at about 2,000 cubic miles (9,000 cubic kilometres).
Cassini, which continues to provide much information and stunning images of Saturn, its rings and its moons, was launched in 1997 and entered Saturn's orbit in 2004. Cassini also carried the European Space Agency's Huygens probe which landed successfully on Titan on January 14, 2005. The Huygens team were relieved and delighted when the small spacecraft landed and started sending back the first data about Titan's surface.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA's Jet Propulsion Laboratory (JPL) based in Pasadena, California, a division of the California Institute of Technology, manages the overall mission for NASA.