Astronomers weekly announce the discovery of new exoplanets, some similar in size or temperature to our planet –- but Earth-like worlds are not always far away.

Though Saturn's largest moon, Titan, is a small, cold world orbiting on the outskirts of the solar system, it actually boasts many familiar features.

“Titan is fascinating because it has some surprising properties so similar to Earth,” said planetary scientist Oded Aharonson from the California Institute of Technology. “It has a liquid which erodes channels, an atmosphere, a hydrologic cycle, and many other parallels.”

Chief among Titan’s interesting qualities is that it's the only body other than Earth where liquids are known to flow in large concentrations on the surface. Because average temperatures there are -300 degrees Fahrenheit, these liquids are not water. Instead, hydrocarbons such as methane and ethane rain down from clouds, course over the landscape in rivers and eventually pour out into large lakes and seas.

The presence of liquids has sparked scientists’ imaginations. If Titan has so many Earth-like features, perhaps it possesses one more terrestrial trait: the presence of life. Native organisms on Titan would be an incredible discovery, showing that life may have formed more than once and suggesting it's common in the universe.

In this gallery, Wired looks closer at the details of this strange wet world so similar and so different from our own.


Sea of Ligeia
Creatively colored in this image, Ligeia Mare looks like an inviting place for a summer vacation. Ligeia is one of Titan’s largest lakes, with a surface area bigger than Lake Superior, located in the planet’s northern high latitudes.

The radar data for this picture came from NASA’s Cassini spacecraft, which has been in orbit around Saturn since 2004. Around the edges, many channels are visible. Rivers of hydrocarbons carved these channels, in much the same way that the Colorado River etched out the Grand Canyon.

Image: Antoine Lucas, Oded Aharonson & The Cassini Radar Science Team, Caltech/JPL/NASA

River Rocks
When the European Space Agency's Huygens lander reached the surface of Titan in 2005, it captured the first-ever evidence of liquid on the surface of another planet. Landing near the edge of a dried lakeshore, it also photographed the rocks seen in the left-hand image.

With their flat shape and rounded edges, the Titan pebbles bear a very strong similarity to rocks from a terrestrial shoreline, suggesting that similar processes generated them.

Image: NASA/JPL/ESA/University of Arizona and S.M. Matheson

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