After a journey of 7 years on board the American Cassini spacecraft the little European space probe Huygens was released on 25 December 2004 and reached the upper layer of Titan's atmosphere on 14 January 2005. After a parachute descent of 2 hours and 28 minutes the probe landed on the mysterious Saturn moon Titan. Now the first results were released by the European Space Agency (ESA).
The data and images from the descent revealing an extraordinary world, resembling Earth in many aspects, especially in meteorology, geomorphology and fluvial activity (maybe liquid methane). Before the Cassini – Huygens Mission reached the Saturn system did not many facts exist but a lot of presumptions because a thick haze veils the moon and the most wavelengths can not penetrate it.
The first radar images from the Cassini orbiter shows a world with bright icy terrain and darker areas that looked like a dry river- or lakebed. Huygens landed in the dark area. Water-ice pebbles up to a few centimetres in diameter were scattered near the landing site, and the surface here was found to have the consistency of loose wet sand.
Another surprise for the scientist were the winds on Titan. Because the winds blow predominantly in the direction of Titan’s rotation, west to east, with speeds up to 450 km/h above an altitude of 120 km. The winds decreased with decreasing altitude and then and changed direction close to the surface. An unexpected layer of high wind-shear was encountered between altitudes of 100 and 60 km.
Huygens also surprised the scientists by finding a second lower ionospheric layer, between 140 km and 40 km, with electrical conductivity peaking near 60 km, and its instruments may also have recorded the signature of lightning.
It was predicted that the atmosphere would be clear of ‘haze’ in the lower stratosphere, but Huygens detected the haze all the way down to the surface. Fortunately, the haze was transparent enough for good images of the surface to be obtained below 40 km.
Other results of the mission confirmed the presence of a complex organic chemistry, which reinforces the idea that Titan is a promising place to observe chemical pathways involving molecules that may have been the building blocks of life on Earth.
The irreversible conversion of methane into other hydrocarbons in Titan's stratosphere implies a surface or subsurface 'reservoir' of methane. Although the Cassini orbiter has not seen a global surface reservoir, and DISR (Descent Imager/Spectral Radiometer) images do not show liquid hydrocarbon pools on the surface either, this instrument's images do reveal the traces of flowing liquid.