Nota de prensa en español
The study links together the recent cloud activity observed in the South Polar Region of Titan with the Cassini/Huygens observations of fluvial features in the surface of the moon. The study is published in the 27th July 2006 number of the journal Nature.
Titan is the largest satellite of Saturn and the second moon in size in the Solar System. With a diameter of 5.150 km is the only moon with a dense atmosphere. The atmosphere itself is mainly composed of nitrogen as the Earth's atmosphere. It is also rich in methane a gas that can condense at the frozen temperatures of Titan (-180ºC). In the upper atmosphere the methane interacts with the faint solar radiation forming a dense haze that fully covers this world veiling its surface and lower atmosphere.
The Cassini spacecraft has performed several flybys of Titan observing its surface with a variety of instruments including radar and cameras observing at specific wavelengths were the haze becomes more transparent. Large Earth based telescopes as the Keck have observed Titan frequently in search of cloud activity which has been recurrent in the Southern Polar Region over the last years and is currently the region of the planet where more sunlight is being received. Besides, the Huygens probe entered the atmosphere of Titan on January 2005 obtaining observations of river channels possibly dry and a wet and soft surface. Besides Earth, Titan could be therefore the only world in the Solar System where liquid deposits may exist in its surface. But how can these fluvial structures form and what is the nature of rain in Titan?
The study of Drs. Ricardo Hueso and Agustín Sánchez-Lavega, from the Basque Country University, proposes that the cloud activity observed is a signature of methane storms. Their numerical simulations of these storms show they can be fairly powerful developing from the 5-10 km height to heights of 30 km above the surface. These storms can produce abundant methane precipitation that would fall in the surface as flash-floods in Earth for the most intense Titan's storms. The powerful rainfalls would generate the wet deposits and river channels of the surface. The research hints to the importance of small particles in the atmosphere required to form the seeds for the precipitation and called cloud condensation nuclei that could be formed in the yellowish-orange haze of the upper atmosphere or lifted from the surface. It is around these particles where methane droplets can form and grow to produce precipitation.
Titan would have a methane meteorological cycle similar to Earth's hydrological cycle.
Although no liquid deposits have already been observed in Titan, their geological signatures have been identified.
The researchers from the University of the Basque Country propose that Cassini radar should observe the regions
where active cloud formation has been recently observed from the ground or the Cassini spacecraft.
Related links:
Relevant articles in Spanish media:
Contact:
Dr. Ricardo Hueso Alonso & Prof. Agustín Sánchez-Lavega
Grupo Ciencias Planetarias
Dpto. Física Aplicada I
Escuela Superior Ingeniería - Universidad País Vasco
Alameda Urquijo s/n
48013 BILBAO (Spain)
Tel. R. Hueso: 94.601.4262
Tel. A. Sánchez-Lavega : 94.601.4255
Fax: 94.601.4178
e-mails: 
, 
http://www.ajax.ehu.es/