Saturn's Moon Titan

Images of Titan taken by NASA's Cassini spacecraft

There are 31 moons orbiting the planet Saturn, but none as interesting as Saturn's largest moon Titan.

Titan has a diameter of 5,150 km (3200 miles). In comparison, Earth's moon only has a diameter of 3,476 km (2,160 miles).

The reason that astronomers find Titan so interesting is that the environmental conditions there may be capable of producing and supporting life due to its thick atmosphere and liquid hydrocarbon lakes.

Astronomers know a lot of about the atmosphere and surface of Titan because images and measurements of the moon were taken during the Voyager and Cassini missions.

The first interesting fact about Titan is that it has a dense atmosphere - even thicker than Earth's atmosphere. The atmosphere on Titan consists mostly of nitrogen, a small amount of argon, and even smaller amounts of carbon dioxide and the hydrocarbons ethane and propane, (Chaisson and McMillan, 2005). Titan is the only moon in our solar system that has a dense atmosphere (Porco, 2005).

Because it is located so far from the Sun, Titan's surface is cold. It has a surface temperature of -290.2 °F (-179 °C). At very cold temperatures like these, liquid hydrocarbons (e.g., methane, propane, ethane) behave like water and so astronomers expected that Titan would have oceans, snow, and rain of hydrocarbons rather than water (Chaisson and McMillan, 2005).

liquid hydrocarbon lakes on Titan

Data from the Cassini mission was consistent with astronomers' expectations. The Cassini spacecraft found liquid hydrocarbon lakes on Titan's surface. The lakes are shown in blue in the NASA image to the right. Astronomers believe that Titan has many more of these liquid hydrocarbon lakes on its surface.

Titan's surface

The image on the left of Titan's surface was taken by the European Space Agency's Huygens probe. Before the probe was delivered by the Cassini spacecraft, scientists had difficulty viewing Titan's surface through its dense atmosphere.

Titan's Internal Structure

Titan's Internal Structure

Scientists believe that Titan has a layer of water ice mixed with ammonia about 100 km (62 miles) below its surface. Based on mass and density measurements, scientists believe that Titan has a rocky core (Porco, 2005).


Chaisson, E. and McMillan, S. (2005). Astronomy Today. Pearson Prentice Hall: Upper Saddle River, NJ.

Porco, Carolyn. "Titan." World Book Online Reference Center. 2005. World Book, Inc.

Images of Titan: Courtesy of NASA/JPL-Caltech.