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Saturn's Titan: Surface change, ammonia, and implications for atmospheric and tectonic activity |
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| Authors: | RM Nelson LW Kamp PGJ Irwin MD Boryta R Jaumann C Sotin DP Cruikshank JC Pearl J Lunine G Bellucci F Capaccioni A Coradini G Filacchione TB McCord PD Nicholson |
| Institution: | a Earth and Space Science Division, JPL/NASA, Mail Stop 183-501, 4800 Oak Grove Drive, Pasadena, CA 91109, USA b Atmospheric, Oceanic and Planetary Physics, Clarendon Laboratory, Parks Road, Oxford, UK c Department of Geology, Mount San Antonio College, Walnut, CA 91789, USA d Institute for Planetary Exploration, DLR, Berlin, Germany e Laboratoire de Planétologie et Géodynamique, University of Nantes, 2 Rue de la Houssinière Nantes, France f US Geological Survey, Mail Stop 964, Box 25046, Federal Center, Denver, CO 80225, USA g NASA AMES, MS 245-6, Mountain View, CA 94035, USA h Observatoire de Paris, 5 Place Jules Janssen, 92195 Meudon, France i Goddard Space Flight Center, MS 693, Greenbelt, MD 20771, USA j University of Pittsburgh, 321 OEH, Pittsburgh, PA 15260, USA k Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA l Office of the Director, Observatoire de Paris, 14eme, 61 Avenue de l'Observatoire, 75014 Paris, France m IASF Istituto Astrofisica Spaziale Fisica Cosmica, Via Fosso Cavaliere 100, 00133 Roma, Italy n Faculté des Sciences, Université de Paris, Sud-Orsay, 91405 Orsay Cedex, France o University of Washington, POB 667, Winthrop, WA 98862, USA p Osservatorio Astronomico di Capodimonte, Salita Moiariello, 16, 80131 Napoli, Italy q Astronomy Department, Cornell University, Space Sciences Building, Ithaca NY 14853, USA |
| Abstract: | Titan is known to have a young surface. Here we present evidence from the Cassini Visual and Infrared Mapping Spectrometer that it is currently geologically active. We report that changes in the near-infrared reflectance of a 73,000 km2 area on Titan (latitude 26° S, longitude 78° W) occurred between July 2004 and March of 2006. The reflectance of the area increased by a factor of two between July 2004 and March-April 2005; it then returned to the July 2004 level by November 2005. By late December 2005 the reflectance had surged upward again, establishing a new maximum. Thereafter, it trended downward for the next three months. Detailed spectrophotometric analyses suggest these changes happen at or very near the surface. The spectral differences between the region and its surroundings rule out changes in the distribution of the ices of reasonably expected materials such as H2O, CO2, and CH4 as possible causes. Remarkably, the change is spectrally consistent with the deposition and removal of NH3 frost over a water ice substrate. NH3 has been proposed as a constituent of Titan's interior and has never been reported on the surface. The detection of NH3 frost on the surface might possibly be explained by episodic effusive events occur which bring juvenile ammonia from the interior to the surface. If so, its decomposition would feed nitrogen to the atmosphere now and in the future. The lateral extent of the region exceeds that of active areas on the Earth (Hawaii) or Io (Loki). |
| Keywords: | Titan Spectrophotometry Infrared observations Ices Spectroscopy |
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