| Titan |
 Titan is the largest satellite of the planet Saturn and the second largest satellite in the solar system. Only Jupiter’s moon Ganymede is larger. Titan has a diameter of 3,200 miles (5,150 kilometers), even larger than the planets Mercury and Pluto. The combination of Titan’s size and its internal density indicates that it probably has a rocky core covered with a shell of water ice. The temperature of Titan’s surface is -290 degrees F ( -179 degrees C). This is so low that no bodies of liquid water on the surface could persist over long periods of time.
Titan is the only satellite in the solar system with a significant atmosphere. In fact, Titan’s atmospheric pressure is about 1.6 times that of Earth. Titan’s surface is almost entirely hidden by its atmosphere, a thick red haze that in some ways resembles the smog found on Earth. About 95 percent of Titan’s atmosphere is nitrogen. Approximately 3 percent is methane, which is a hydrocarbon (a compound of hydrogen and carbon). The remaining 2 percent consists of hydrogen, other hydrocarbons, and possibly argon. Little water vapor exists in the satellite’s atmosphere. Hydrocarbons may rain down on the surface, forming enclosed seas, lakes, and ponds. Voyager 1 and Voyager 2, two space probes launched by the United States, provided information about Titan in 1980 and 1981. The Cassini spacecraft, which began orbiting Saturn in the summer of 2004, carried cloud-penetrating radar and other instruments designed to “see” through Titan’s atmosphere. It also carried a probe called Huygens that was designed to drop through Titan’s atmosphere and land on its surface. Contributor: Carolyn Porco, Ph.D., Professor, Cussini Imaging Central Laboratory for Operations, Southwest Research Institute. Info provided by: Porco, Carolyn. “Titan.” World Book Online Reference Center. 2005. World Book, Inc. http://www.worldbookonline.com/wb/Article?id=ar559220 |