Titan (tye'-t?n, IPA: ['ta?tn?], Greek ??t??) or Saturn VI is the largest moon of Saturn and the second largest moon in the solar system, after Jupiter's moon Ganymede. It is roughly 50% larger than Earth's moon by diameter, and is larger by diameter and mass than all known dwarf planets. It is also larger by diameter than the planet Mercury, though Mercury is more than twice as massive.
Titan is the only moon in our solar system to have a dense atmosphere. Until very recently, this atmosphere inhibited understanding of Titan's surface, but the moon is currently undergoing study by the Cassini-Huygens mission, and new information about it is accumulating, such as the discovery of liquid hydrocarbon lakes near its north pole.
Titan was discovered on March 25, 1655 by the Dutch astronomer Christiaan Huygens, and was the first moon in the Solar System to be discovered after the Galilean moons of Jupiter.
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