  Saturn's largest satellite, Titan, has stratospheric wind speeds that may be
up to ~210 m/sec [1], circling Titan in about a day compared to Titan's slow
16-day rotation. Theoretical models to explain such super-rotating winds are
not well constrained [2,3,4,5,6] by observations of Titan or a similar slow
rotator, Venus. Titan's stratospheric temperature and the abundance of the
important constituent ethane (C2H6) should be zonally invariant due to long
photochemical and radiative lifetimes and rapid transport and mixing by high
zonal winds. Here, we report new measurements of zonal wind in Titan's
equatorial region, including the Cassini Huygens probe entry latitude [7].
Prograde zonal winds of 190+/-90 m/sec are found from Doppler-shifted ethane
gas infrared emission near 12 micron wavelength, confirming high wind velocity
even near the equator. Surprisingly, we find a temperature difference of 6+/-3
K between the East and West hemispheres of Titan at ~240 km altitude. Common
direct processes such as diurnal heating by sunlight do not adequately explain
the asymmetry, suggesting other processes, such as unknown atmospheric
dynamics, may be responsible. The origin of the temperature difference is
enigmatic and currently unexplained.
