Titan has about 9000 cubic kilometers of liquid hydrocarbon, some forty times more than in all the proven oil reservoirs on Earth. That’s just one of the findings of scientists working over the data from recent Cassini flybys of the Saturnian moon. Each flyby snares our attention because this is the only other place in the Solar System that has stable liquid on the surface, even if it’s not water. That’s part of Titan’s fascination, of course, because it’s similar to the Earth in terms of basic interactions between liquids, solids and gases but completely alien in terms of temperatures.
Just how extensive are those seas and lakes we’ve found in Titan’s northern hemisphere? Cassini’s radar instrument has given us our best views to date with the mosaic shown below, one that’s based on multiple images from flybys tracking areas at various angles. Kraken Mare, Titan’s largest sea, and Ligeia Mare, the second largest, appear along with nearby lakes. We learn not only that Kraken Mare is more extensive than first thought, but that almost all the lakes on Titan are in an area some 900 kilometers by 1800 kilometers. A mere three percent of the liquid on Titan is found outside this region. Cassini radar team member Randolph Kirk explains:
“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.”
This JPL news release adds that processes like these on Earth lead to the formation of faults that create basins broken by mountain ranges. Much of present day Nevada was, some 13,000 years ago, flooded by Lake Lahontan in a configuration that resembles, on a smaller scale, Titan’s closely packed seas.
Image: This colorized mosaic from NASA’s Cassini mission shows the most complete view yet of Titan’s northern land of lakes and seas. In this projection, the north pole is at the center. The view extends down to 50 degrees north latitude. In this color scheme, liquids appear blue and black depending on the way the radar bounced off the surface. Land areas appear yellow to white. A haze was added to simulate the Titan atmosphere. Kraken Mare, Titan’s largest sea, is the body in black and blue that sprawls from just below and to the right of the north pole down to the bottom right. Ligeia Mare, Titan’s second largest sea, is a nearly heart-shaped body to the left and above the north pole. Punga Mare is just below the north pole. Credit: JPL.
Note the smaller lakes above and to the left of the north pole, which are about 50 kilometers across or less. Moreover, the new data are finally telling us how deep at least one of the seas is. Because the liquid methane of Ligeia Mare is very pure, Cassini’s radar signal passes through it easily and can detect a signal from the sea floor. The lake turns out to be about 170 meters deep, and in at least one place is deeper than the average depth of Lake Michigan. With northern summer approaching, Titan’s lake country should be entering an interesting meteorological phase for Cassini’s future studies as the atmosphere heats up.