Huygens probe on the surface of Titan, artwork. Titan is the largest moon of the planet Saturn. The 1.3-metre-wide Huygens probe, released by the Cassini spacecraft, entered Titan's atmosphere on 14 January 2005. The descent to the surface by parachute (on ground at upper left) took 2.5 hours, during which time the probe sent back pictures and sound. Instruments were used to record the composition of Titan's atmosphere and surface. The atmosphere is mainly nitrogen with clouds of methane and ethane. The surface is a mixture of water and hydrocarbon ice. The surface temperature can reach -180 degrees Celsius. The Huygens probe was launched from Earth in 1997.