Huygens probe. Computer artwork of the Huygens probe descending through the atmosphere of Titan, the largest moon of the planet Saturn (orange disc at upper left). The Huygens probe was released by the Cassini spacecraft in December 2004, entering Titan's atmosphere on 14 January 2005. The descent to the surface by parachute took 2.5 hours, and the probe sent back pictures and sound. Instruments were used to record the composition of Titan's atmosphere and surface. Observations confirmed that the atmosphere is mainly nitrogen with clouds of methane and ethane. The surface is a dirty mixture of water and hydrocarbon ice. The surface temperature is about -180 degrees Celsius.