Titan’s wintry Wonderland
06 December 2005
On 14 January 2005 ESA's Huygens probe made an historic landing on the surface of Saturn's giant satellite, Titan. Now, after careful analysis of the Huygens data, scientists have unravelled many of the mysteries of this planet-sized moon.
During its 2 ½ hour descent, instruments recorded details of temperature, wind speed and atmospheric composition. The results show that Huygens had a bumpy ride as it was blown eastward by high level winds of more than 100 km per hour. However, as it drifted down through the orange haze, the temperature and density of the atmosphere increased and the wind speed fell. The winds reversed direction at a height of 7 km, carrying Huygens gently westward during the final minutes of the descent.
The atmosphere was mostly nitrogen, with about 5 per cent methane, and the haze in the atmosphere was also mainly made of methane. (On Earth, methane gas is burnt in boilers and cookers.)
The 350 or so images collected during the mission revealed an icy landscape marked by dark channels snaking towards a smooth ‘shoreline’. Methane rainstorms sometimes fill the dry channels, creating temporary rivers that erode the surface and carry loose material onto nearby plains.
The flat lowland site where Huygens touched down was sprinkled with pebbles or small chunks of ice. Although the surface was fairly soft, rather like lightly packed snow, it was extremely cold (-180C) – much colder than Antarctica. The fine-grained ice was wet with methane, which evaporated when touched by the warm probe.