It's bigger than Mercury, has dune seas like Tatooine (or Arrakis) and has the coolest name of any moon: Titan. The Cassini spacecraft is still revealing many of its secrets, with another flyby scheduled just a few weeks from now. Here are five reasons to get excited about Saturn's largest satellite.
1. Titan is the only moon with a thick, stable atmosphere. It's mostly made of nitrogen, with a decent helping of methane and other hydrocarbons. It's not exactly a breathable atmosphere, but it's still pretty cool. Even better, Titan has Earth-like weather. Wind and rain sweep the surface of Titan, shaping its geography and producing seasonal effects. Some scientists say Titan is a lot like a young Earth, only much colder.
2. Titan has dune seas. As much as 40 percent of the equatorial region might be covered by "sand" dunes hundreds of meters high. They probably aren't made of silicate particles the way Earth sand is. Rather, Titan's sand could be precipitated from the atmosphere. The dunes are sort of like semi-permanent snow drifts.
3. Titan has cryovolcanoes. There are mountains on Titan, along with evidence of volcanic activity. The interior of Titan probably doesn't support the same kind of heat and pressure that we find within the Earth. Instead, Titan's volcanoes might be the result of highly pressurized ice fracturing and spewing liquid water and ammonia into the atmosphere.
4. Titan has liquid features on the surface, like the hydrocarbon lakes pictured in the computer rendering above. Earlier Cassini data found proof of methane lakes in Titan's polar regions. Even more interesting, there might be an entire ocean lying beneath Titan's surface. This leads us to the best reason that Titan is awesome...
5. Titan might be our best bet for finding extraterrestrial life within our solar system. If the subsurface ocean exists, it would be made of liquid water and ammonia and would be warmer than the surface. The chemical makeup of the atmosphere and the active weather and geology have lead some scientists to propose that the conditions on Titan are right for the formation of primitive life. That's exciting. Image by Steven Hobbs via NASA.