Lakes on Titan
Minnesota is called the land of 10,000 lakes for good reason: There are natural pools of water everywhere. Scientists have long thought that liquid-rich lands such as Minnesota are unique to planet Earth. New evidence suggests otherwise.
Recent radar images show that Saturn's moon Titan has lakes, too. The liquid in Titan's lakes isn't water, however. It's a substance called methane. Still, this is the first evidence that bodies of liquid exist anywhere in the solar system besides Earth.
The dark patches seen in this radar image of Titan's north polar region are probably methane lakes.
In the new images, Titan's north polar region looks a lot like Minnesota. Underneath the moon's atmospheric haze, there are lots of lake-shaped, dark areas with channels running between them. There are also signs of shorelines and wind-driven waves.
The smallest lakes are less than a kilometer (0.6 mile) wide. The largest is 90 kilometers (56 miles) wide. NASA's Cassini spacecraft took the images on July 22. Cassini has been in orbit around Saturn since 2004.
It's bitterly cold on Titan. At –180 degrees Celsius (–292 degrees F), any water there would freeze instantly. Instead, Titan's lakes are probably filled with liquid methane and maybe some ethane. These substances are known as hydrocarbons.
Methane makes up 5 percent of Titan's atmosphere, but the hydrocarbon breaks down over time when exposed to sunlight. Scientists suspect that methane moves back and forth between the atmosphere and the surface of Titan, just like water cycles between ground and sky on Earth.
Other parts of Titan's north polar region also show evidence of methane lakes.
These observations support the idea that Titan is similar to what Earth was probably like long before life started here.
A few more flybys should confirm whether the moon is Minnesota-like or not. In October, Cassini's radar system will capture images of Titan's north pole from a different angle. Then, in 2008, it will take radar images of the moon's south pole.—E. Sohn
Cowen, Ron. 2006. Titan's lakes: Evidence of liquid on Saturn's largest moon. Science News 170(Aug. 5):83. Available at http://www.sciencenews.org/articles/20060805/fob1.asp .
For additional information about lakes on Titan, go to www.nasa.gov/mission_pages/cassini/multimedia/pia08630.html (NASA).
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Sohn, Emily. 2005. Sounds of Titan. Science News for Kids (Feb. 16). Available at http://www.sciencenewsforkids.org/articles/20050216/Feature1.asp .
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