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Science 13 May 2005:
Vol. 308. no. 5724, pp. 978 - 982
DOI: 10.1126/science.1111790
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Reports

The Cassini UVIS Stellar Probe of the Titan Atmosphere

Donald E. Shemansky,1* A. Ian F. Stewart,2 Robert A. West,3 Larry W. Esposito,2 Janet T. Hallett,1 Xianming Liu1

The Cassini Ultraviolet Imaging Spectrometer (UVIS) observed the extinction of photons from two stars by the atmosphere of Titan during the Titan flyby. Six species were identified and measured: methane, acetylene, ethylene, ethane, diacetylene, and hydrogen cyanide. The observations cover altitudes from 450 to 1600 kilometers above the surface. A mesopause is inferred from extraction of the temperature structure of methane, located at 615 km with a temperature minimum of 114 kelvin. The asymptotic kinetic temperature at the top of the atmosphere determined from this experiment is 151 kelvin. The higher order hydrocarbons and hydrogen cyanide peak sharply in abundance and are undetectable below altitudes ranging from 750 to 600 km, leaving methane as the only identifiable carbonaceous molecule in this experiment below 600 km.

1 Department of Aerospace Engineering, University of Southern California, University Park, Los Angeles, CA 90089, USA.
2 University of Colorado, Laboratory for Atmospheric and Space Physics, Boulder, CO 80303, USA.
3 Jet Propulsion Laboratory, Pasadena, CA 91109, USA.

* To whom correspondence should be addressed. E-mail: dons{at}hippolyta.usc.edu

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Inaugural Article: Organic haze on Titan and the early Earth.
M. G. Trainer, A. A. Pavlov, H. L. DeWitt, J. L. Jimenez, C. P. McKay, O. B. Toon, and M. A. Tolbert (2006)
PNAS 103, 18035-18042
   Abstract »    Full Text »    PDF »
Intensive Titan Exploration Begins.
P. R. Mahaffy (2005)
Science 308, 969-970
   Abstract »    Full Text »    PDF »


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