Huygens probe at Titan. Artist's impression of the Huygens probe just above the surface of Titan, the largest moon of Saturn. The surface is shown covered in organic ices and a lake of liquid ethane. After entering the atmosphere Huygens will descend under a large main parachute to allow upper atmosphere measurements. This will then be discarded, and Huygens will drop more rapidly under this 3-metre secondary parachute to the surface. The descent will take about 2 1/2 hours, and Huygens will hit the surface at a speed of 7 metres per second. Huygens is a European project, part of NASA's Cassini spacecraft, and will arrive at Titan on 27 November 2004.