Compositional evidence for Titanʹs stratospheric tilt

Five years of Cassini CIRS infrared spectra have been used to determine the tilt of Titanʹs stratospheric symmetry axis with respect to the solid body rotation axis. Measurements of HCN abundance centred around 5 mbar (125 km altitude) at equatorial latitudes show the symmetry axis is tilted by 4.0 ± 1 . 5 ∘ in a direction 70 ± 40 ∘ W of the sub-solar point. This value is consistent with tilts determined from temperature and haze measurements by Achterberg et al. (2008a) and Roman et al. (2009). The consistency of results from three independent methods suggests that Titanʹs entire stratosphere is tilted and provides a powerful constraint on the underlying atmospheric dynamics.