Document Detail


Active upper-atmosphere chemistry and dynamics from polar circulation reversal on Titan.
MedLine Citation:
PMID:  23192150     Owner:  NLM     Status:  In-Process    
Abstract/OtherAbstract:
Saturn's moon Titan has a nitrogen atmosphere comparable to Earth's, with a surface pressure of 1.4 bar. Numerical models reproduce the tropospheric conditions very well but have trouble explaining the observed middle-atmosphere temperatures, composition and winds. The top of the middle-atmosphere circulation has been thought to lie at an altitude of 450 to 500 kilometres, where there is a layer of haze that appears to be separated from the main haze deck. This 'detached' haze was previously explained as being due to the co-location of peak haze production and the limit of dynamical transport by the circulation's upper branch. Here we report a build-up of trace gases over the south pole approximately two years after observing the 2009 post-equinox circulation reversal, from which we conclude that middle-atmosphere circulation must extend to an altitude of at least 600 kilometres. The primary drivers of this circulation are summer-hemisphere heating of haze by absorption of solar radiation and winter-hemisphere cooling due to infrared emission by haze and trace gases; our results therefore imply that these effects are important well into the thermosphere (altitudes higher than 500 kilometres). This requires both active upper-atmosphere chemistry, consistent with the detection of high-complexity molecules and ions at altitudes greater than 950 kilometres, and an alternative explanation for the detached haze, such as a transition in haze particle growth from monomers to fractal structures.
Authors:
Nicholas A Teanby; Patrick G J Irwin; Conor A Nixon; Remco de Kok; Sandrine Vinatier; Athena Coustenis; Elliot Sefton-Nash; Simon B Calcutt; F Michael Flasar
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Nature     Volume:  491     ISSN:  1476-4687     ISO Abbreviation:  Nature     Publication Date:  2012 Nov 
Date Detail:
Created Date:  2012-11-29     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0410462     Medline TA:  Nature     Country:  England    
Other Details:
Languages:  eng     Pagination:  732-5     Citation Subset:  IM    
Affiliation:
School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol BS8 1RJ, UK. n.teanby@bristol.ac.uk
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