With its dense atmosphere and ice, Saturn’s largest moon fascinates scientists. It would present conditions favorable to the development of life.

In line of sight, there is the Moon then Mars. But behind, another star that depends on our star is now the focus of scientists’ attention: Titan. This “little” moon of Saturn fascinates. First, by its size (5,150 kilometers in diameter) which makes it bigger than the planet Mercury. Then by its dense atmosphere, the only one in the solar system to be as developed as ours with a pressure of 1.5 bar (against 1 for the Earth) and a record thickness – between 200 and 800 kilometers above sea level. “Titan is developing a similar climate system where exchanges between the surface and the atmosphere are intense”, summarizes Alice Le Gall, from the University of Paris-Saclay, and researcher at the Atmospheres, Environments, Space Observations (Latmos) laboratory. With one detail: the surface of the blue planet is dominated by rocks and water, when that of Saturn’s moon is made up of ice and the main liquid element remains methane. But this complex carbonaceous organic chemistry is the dream of exobiologists since it could shelter the conditions necessary for the development of life.

Scanned by a host of terrestrial telescopes, Titan, because of its dense atmosphere, is not easily revealed. Hence the purpose of the American-European Cassini-Huygens mission which explored it as closely as possible between 2004 and 2017. Three years later, astronomers are still using the data from the radar and infrared spectrometer of the probe resulting from of 120 overflights. “We have succeeded in mapping 65% of the surface with a resolution of 300 meters at 4 kilometers”, explains Alice Le Gall who, within an international team led by the California Institute of Technology (Caltech) in the United States, has drew up the first geomorphological map of Titan.

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