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[20.16] Spatially Resolved Millimeter and Submillimeter Observations of Molecules in Titan's Atmosphere

M.A. Gurwell (CfA), B.J. Butler (NRAO), D.O. Muhleman (Caltech)

High spatial and spectral resolution observations of Titan utilizing three interferometric arrays were obtained to measure the horizontal and vertical distributions of several molecular species.

(1) SMA \lambda=0.85 mm observations performed Feb 2004 slightly resolved Titan (beam ~0.7 arcsec, Titan 0.89 arcsec). Transitions of CO, HCN, HC¹⁵N, H¹³CN, and HC₃N were observed; analysis of global average abundances are provided in Gurwell 2004. The HCN species show a latitudinal gradient even at this coarse resolution, with higher abundances in the northern hemisphere. No gradient in CO abundance was detected.

(2) OVRO \lambda=1.25 mm observations performed Dec 2000 achieved ~0.4 arcsec resolution (Titan was 0.9 arcsec), and detail large abundance gradients for CH₃CN and HC₃N in the upper atmosphere. CH₃CN emission is 3-5 times stronger over the southern pole than elsewhere on the observed disk, and also shows enhancement on the western (evening) limb. This could suggest photochemical production in the sunlit atmosphere that occurs in a large scale prograde zonal jet. HC₃N was only detected at high northern latitudes and (less strongly by a factor of 2) over the southern pole. CH₃CCH and C₃H₂ were not detected, with upper limits about an order of magnitude less than the predicted photochemical model profiles from Toublanc et al. (1995).

(3) VLA \lambda=7.12 mm observations performed Nov 1999 provided the highest resolution radio maps of Titan ever obtained (~0.2 arcsec). Surface imaging analysis is provided in Butler & Gurwell (this meeting). The simple carbon ring C₃H₂ was not detected, with an upper limit more than an order of magnitude less than the Toublanc et al. (1995) profile, consistent with that found in (2).

References: Gurwell 2004, ApJL, in press. Toublanc et al. 1995, Icarus 113, 2-26.

MAG gratefully acknowledges support for from NASA Planetary Astronomy grant NAG5-7946.

The author(s) of this abstract have provided an email address for comments about the abstract: mgurwell@cfa.harvard.edu

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