Titan's stratospheric zonal wind, temperature, and ethane abundance a year prior to Huygens insertion

doi:doi:10.1029/2005GL023897

Abstract

T. Kostiuk

NASA Goddard Space Flight Center, Greenbelt, Maryland, USA

T. A. Livengood

NASA Goddard Space Flight Center, Greenbelt, Maryland, USA

T. Hewagama

NASA Goddard Space Flight Center, Greenbelt, Maryland, USA

G. Sonnabend

National Research Council, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA

K. E. Fast

NASA Goddard Space Flight Center, Greenbelt, Maryland, USA

K. Murakawa

Subaru Telescope, National Astronomical Observatory of Japan, Hilo, Hawaii, USA

A. T. Tokunaga

Institute for Astronomy, University of Hawaii, Honolulu, Hawaii, USA

J. Annen

NASA Goddard Space Flight Center, Greenbelt, Maryland, USA

D. Buhl

NASA Goddard Space Flight Center, Greenbelt, Maryland, USA

F. Schmülling

I. Physikalisches Institut, Universität zu Köln, Cologne, Germany

Saturn's satellite, Titan, may have stratospheric winds up to ∼210 m/s, circling Titan in ∼1 terrestrial day compared to its 16-day rotation. Theoretical models explaining such super-rotating winds are not well constrained by observations of Titan or a similar slow rotator, Venus. We report measurements taken in December 2003 of zonal wind near Titan's equatorial region, including the Cassini Huygens probe entry latitude. Super-rotating prograde zonal winds of 190 ± 90 m/s near 220 km altitude are found from Doppler-shifted C₂H₆ gas emission near 12 μm, confirming high wind velocity even near the equator. Stratospheric temperature constraints and ethane abundance (8 ± 3 ppm) also are retrieved. Results are not inconsistent with earlier measurements and with recent Cassini CIRS results, but indicate possible variations between Titan's hemispheres. Differences in east and west C₂H₆ spectral line shapes can be accounted for by different vertical distributions of either C₂H₆ abundance or temperature or by unidentified dynamical effects.

Received 23 June 2005; accepted 28 September 2005; published 30 November 2005.

Citation: Kostiuk, T., T. A. Livengood, T. Hewagama, G. Sonnabend, K. E. Fast, K. Murakawa, A. T. Tokunaga, J. Annen, D. Buhl, and F. Schmülling (2005), Titan's stratospheric zonal wind, temperature, and ethane abundance a year prior to Huygens insertion, Geophys. Res. Lett., 32, L22205, doi:10.1029/2005GL023897.

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