High-Resolution Image

Saturn's moon Titan was discovered in 1655, by Christian Huygens. Shown are two recent views of a Titan "shoreline", taken by the European Space Agency's Huygens probe that was transported to Titan by the Cassini spacecraft, that launched in fall 1997. Titan's surface temperature is measured to be about 94K = -178¡C = -289¡F so this is not a "beach" where you might suntan!

Methane may be marginally below its saturation pressure of 1600 mb near Titan's surface, so that methane rivers, lakes and oceans may not exist per se. But rivers, lakes, perhaps even oceans of ethane can exist in which methane may be dissolved. (Methane is also an important "greenhouse gas" in Earth's atmosphere, where like carbon dioxide it is present in only trace amounts, but its increasing concentration is thought to contribute to global warming).

One model for the Titan atmosphere is 62% nitrogen, 21% methane, and 17% argon, with surface pressure roughly 50% higher than Earth's. Another model has it at 95% nitrogen, 3% methane, and 2% argon and trace hydrocarbons, like Earth's smog. Science fiction author Arthur C. Clarke wrote in "Imperial Earth" that methane, a fuel on Earth, and oxygen, needed to make methane combustible, may reverse their roles on Titan, with oxygen becoming the fuel, and methane the gaseous additive needed for fire. Methane photolysis on Titan can produce heavier hydrocarbons Ð ethane, acetylene, ethylene, and with nitrogen, hydrogen cyanide, one building block of amino acids. The Titan images will continue to improve over the coming year as the processing continues, and analysis of the data will improve our understanding of Titan for the next several years. We will soon have a better understanding of Titan's atmosphere, and the processes of rainfall, river runoff, and erosion suggested by the Earth-like surface features seen in the early images from Huygens.

[A pre-Cassini review of Titan surface processes is here. See also Lunine. J.I. Does Titan Have an Ocean? A Review of Current Understanding of Titan's Surface. Review of Geophysics., 31(2). p133-149. (1993). Photo credits: ESA, NASA, Descent Imager/Spectral Radiometer Team, LPL. Caption submitted by R. Cahalan]