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[20.10] Stratospheric Abundances Of C₂H₂ and C₂H₆ In Titan's Southern Hemisphere From Cassini CIRS Spectra

C.A. Nixon (University of Maryland), P.N. Romani, G.L. Bjoraker (NASA GSFC), P.G.J. Irwin, N. A. Teanby (University of Oxford), F.M. Flasar (NASA GSFC), Cassini CIRS Team

On July 2nd 2004, the Cassini spacecraft made its first, distant (340,000 km) fly-by of Saturn's enigmatic moon Titan. The Composite Infrared Spectrometer (CIRS) was used to map the southern hemisphere in the mid-infrared (600--1400 cm^-1). The mid-IR capability of CIRS is achieved through a Michelson spectrometer and two 1\times10 detector arrays. The arrays consist of square pixels with a 0.273 mrad FOV width, giving a spatial resolution on the disk of 92--109 km (2.0^\circ--2.4^\circ of great circle arc) during the mapping sequence. An intermediate spectral resolution of FWHM=2.5 cm^-1 was chosen to give the best compromise between integration time (spatial resolution) and spectral resolution.

This presentation will focus on the abundances of C₂H₂ and C₂H₆ from equator to south pole. Both gases are sounded in the stratosphere, via the \nu₅ and \nu₉ bands centered on 729 and 821 cm^-1 respectively. Meridional variations of ethane and acetylene have previously been determined from Voyager 1 IRIS spectra, taken some 23 years, 3.2 Titan seasons earlier (Coustenis et al 1995), and at a lower spectral resolution of FWHM=4.3 cm^-1. Similarities and differences between the IRIS results and the present CIRS determination will be discussed.

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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.