Saturn's Titan: Surface change, ammonia, and implications for atmospheric and tectonic activity

doi:10.1016/j.icarus.2008.08.013

Authors

Contributors

Jet Propulsion Laboratory (JPL); NASA-California Institute of Technology (CALTECH); Department of Atmospheric, Oceanic and Planetary Physics Oxford (AOPP); University of Oxford; Department of Geology, Mount San Antonio College; Mt. San Antonio College (Mt. SAC); Department of Planetary Exploration, DLR; Laboratoire de Planétologie et Géodynamique de Nantes UMR 6112 (LPGN); Université de Nantes (UN)-Centre National de la Recherche Scientifique (CNRS); US Geological Survey, Denver; National Aeronautics and Space Administration, Ames Research Center; Observatoire de Paris; Centre National de la Recherche Scientifique (CNRS)-Université Paris Sciences et Lettres (PSL); Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA); Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris; Centre National de la Recherche Scientifique (CNRS)-Université Paris Sciences et Lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Sciences et Lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS); Pôle Planétologie du LESIA; Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA); Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris; Centre National de la Recherche Scientifique (CNRS)-Université Paris Sciences et Lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Sciences et Lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris; Centre National de la Recherche Scientifique (CNRS)-Université Paris Sciences et Lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Sciences et Lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité); NASA Goddard Space Flight Center (GSFC); University of Pittsburgh; Lunar and Planetary Laboratory University of Arizona (LPL); University of Arizona; Istituto di Astrofisica Spaziale e Fisica Cosmica (IASF-Roma); Institut d'astrophysique spatiale (IAS); Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales Paris (CNES); University of Washington, Winthrop; INAF-Osservatorio Astronomico di Capodimonte (INAF-OAC); Department of Astronomy, Cornell University + 29

Published in

ISSN: 0019-1035

Publisher

CCSD; Elsevier

Abstract

International audience ; 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 km 2 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 H 2 O, CO 2 , and CH 4 as possible causes. Remarkably, the change is spectrally consistent with the deposition and removal of NH 3 frost over a water ice substrate. NH 3 has been proposed as a constituent of Titan's interior and has never been reported on the surface. The detection of NH 3 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).