Titan, Saturn's largest moon, is the second largest moon in the Solar System. The diameter of Titan is 5150 km, in comparison, the Earth is 12 756.28 km. In its thick atmosphere, Cassini's infrared spectrometer has observed a huge cloud system covering the north pole of Titan. Titan is the only moon in the Solar System to possess a thick atmosphere of nitrogen (dinitrogen) and methane clouds, in which one can observe a very active weather (evaporation, cloud formation, precipitation of methane). Its atmosphere is 10 times denser than Earth's atmosphere and receives 100 times less solar energy, its mean temperature is about -180 ° C. Titan has, like the Earth, the seasons very marked because of the high inclination of its axis of rotation. Ten times farther from the Sun than Earth, Titan takes 29 years to orbit the Sun. Its seasons last about 7 years. The study of Titan in the coming years, we may reveal surprises about unimaginable ways, that life can take.
Image: Sight of Titan by the mission Cassini, on October 26th, 2004. This mosaic of 9 images shows variations of brightness of Titan's surface, and brilliant clouds near the south pole. The most brilliant region of the right-hand side and the equatorial region carry the name of Xanadu. Surface seems young and there is no visible crater.
5 152 ±2 km
March 25, 1655
1 186 680 km
1 257 060 km
1 221 870 km
synchronous with Saturn
0.34854° to Saturn's equator
Titan 146.7 kPa Earth 101.3 kPa
98.4% nitrogen (N2) 1.4% methane (CH4)
95.4% nitrogen (N2) 4.9% methane (CH4)
Seas of Titan
As its lakes, the seas of Titan are probably constituted by methane and by ethane liquid in the steep banks. One of its liquid surfaces extends over 100 000 square kilometers, the Lake Superior one of the biggest on Earth is 82 000 square kilometers. Vast liquid areas were observed by the radar of the space probe Cassini on February 22nd, 2007 what supplies a strong indication on the sea existence on the biggest moon of Saturn (see opposite). The radar data analysis of these images besides lets suppose depths which can reach several tens of meters. For these reasons, the scientists decided to classify these surfaces as seas. The biggest liquid seas are situated in Titan's highest latitudes, most being situated in the North of the 70th parallel of this cold and distant world.
Image: The radar instrument of the space probe Cassini is a system hyper-frequencies which allows to study Titan's surface through its opaque atmosphere. This instrument works in mode radio measure, scatterometer, altimeter and imager SAR (Synthetic Aperture Radar). It is this last mode which allows to observe Titan's surface with a resolution better than measures in kilometers it.
Surface of Titan
On January 14, 2005, after a seven-year journey through the Solar System, the Cassini spacecraft, descended through Titan's atmosphere, successfully landing on its surface. "It is a great achievement for Europe and its American partners in this ambitious international effort to explore the Saturnian system," said Jean-Jacques Dordain, Director General of ESA. The probe started its descent through layers of Titan's hazy cloud at an altitude of about 1270 km at 11:13 CET. During the following three minutes Huygens had to slow down from 18000 last 1400 km per hour. A parachute has slowed to less than 300 km per hour. At a height of about 160 km scientific instruments of the mission have been exposed to the atmosphere of Titan. At about 120 km, the main parachute was replaced by a smaller one to complete the descent, with landing expected at 13:34 CET. The landscape of Titan have similarities with those of the Earth, said Martin G. Tomasko, in charge of DISR, the instrument that took the pictures. Fog, traces of precipitation, erosion, mechanical abrasion, networks of drainage channels, river systems, lakes drained, coastal landscapes and strings of islands, "the physical processes shaping Titan are very similar to those that have shaped the Earth. The materials, however, are more "exotic" Martin Tomasko of the ESA. Since water (H20) is replaced by methane (CH4), which can exist in liquid or gas at Titan's surface. When it rains, it rains are methane mixed with traces of oil are deposited on the ground.
Image: an excerpt from the soundtrack, captured by Huygens on the surface of Titan
Rains would also fallen "in a not too distant past," said Martin Tomasko yet, January 21, 2005. Titan has so much atmosphere uniform made of different gases (methane, nitrogen ,...), on the frozen ground to -180 ° C, there is a cryo volcanic activity, rivers and water in abundance and of countless pebbles of ice as big as cars.
Image: The surface of Titan, photographed by the European probe Cassini Huygens January 14, 2005. Credit ESA, in partnership with NASA, JPL, University of Arizona. Picture taken during the descent of the probe to the surface of Titan. Below, a video simulated images from Huygens, descent of the probe through the thick opaque atmosphere of Titan.
Thetis behind Titan
The two moons of Saturn, one behind the other were captured by the Cassini spacecraft. What is the star in the background behind Titan? Tethys is another moon of Saturn. The Cassini spacecraft at the end of 2009, has immortalized this icy moon, heavily cratered as it passed behind the thick atmosphere of Titan. It differs completely Odysseus, the largest crater (450 km wide) of Tethys, whose diameter is about 1000 km. Titan, with its diameter of 5100 km Revel here in the foreground, its opaque orange atmosphere, and his strange blue haze layer that halo its upper atmosphere. When this picture was taken, Tethys was twice as far as Titan from Cassini. Tethys was approximately 2 million kilometers.
At the end of 2004, Cassini released the European probe Huygens on Titan. The probe landed on 15 January 2005 and gave mankind the very first images of the surface of the only moon in the solar system known to be partially covered with lakes of hydrocarbons.
Image: The Cassini spacecraft used to study Titan's surface through its opaque atmosphere.