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Dissipation of Titan's north polar cloud at northern spring equinox |
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| Authors: | Stéphane Le Mouélic Pascal Rannou Sébastien Rodriguez Christophe Sotin Caitlin A Griffith Lucille Le Corre Jason W Barnes Robert H Brown Kevin H Baines Bonnie J Buratti Roger N Clark Philip D Nicholson Gabriel Tobie |
| Institution: | 1. Laboratoire de Planétologie et Géodynamique, CNRS, UMR6112, université de Nantes, 2 rue de la Houssinière, BP92208, 44322 Nantes cedex 3, France;2. GSMA, Université de Reims, France;3. Laboratoire AIM, CEA, Gif/Yvette, France;4. JPL, Pasadena, USA;5. Lunar and Planetary Lab and Steward Observatory, University of Arizona, Tucson, USA;6. Department of Physics, University of Idaho, Engineering–Physics Building, Moscow, ID 83844, USA;7. USGS, Denver, USA;8. Cornell University, USA |
| Abstract: | Saturn's Moon Titan has a thick atmosphere with a meteorological cycle. We report on the evolution of the giant cloud system covering its north pole using observations acquired by the Visual and Infrared Mapping Spectrometer onboard the Cassini spacecraft. A radiative transfer model in spherical geometry shows that the clouds are found at an altitude between 30 and 65 km. We also show that the polar cloud system vanished progressively as Titan approached equinox in August 2009, revealing at optical wavelengths the underlying sea known as Kraken Mare. This decrease of activity suggests that the north-polar downwelling has begun to shut off. Such a scenario is compared with the Titan global circulation model of Rannou et al. (2006), which predicts a decrease of cloud coverage in northern latitudes at the same period of time. |
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