As the Cassini spacecraft orbits the Saturn system, it is showing astronomers that Saturn's largest moon, Titan, has many weather and geologic features that are similar to Earth's.
Titan is the only other satellite in the solar system to have a thick atmosphere, and it is the only other world to possess surface liquid. Methane on Titan is analogous to the water cycle on Earth, with evaporation, cloud formation, and precipitation. Scientists believe Titan's nitrogen-rich atmosphere and methane and ethane lakes could possibly harbor microbial extraterrestrial life.