Titan Stratospheric Haze Bands Observed in Cassini VIMS as Tracers of Meridional Circulation

We analyzed Cassini data to derive the nature and evolution of circumglobal annuli observed in the stratosphere of Titan, Saturn's largest moon. The annuli were observed between 2004 and 2017 in data acquired by the Visual and Infrared Mapping Spectrometer on board the Cassini spacecraft. We observed a north polar annulus, an equatorial annulus, and several secondary annuli. Pre-Cassini telescopic observations by the Hubble Space Telescope and Keck reported an atmospheric feature consistent with the presence of a south polar annulus between 1999 and 2001, although this feature was not observed by Cassini. Relative to the atmosphere near the annuli, they appear dark at 300-500 nm and bright in methane absorption channels such as the ones at 900 and 1150 nm. The stratosphere seems to rotate around the north pole. Alternatively, it seems to rotate about a point offset from solid-body rotation axis by a few degrees; this point in turn rotates around the solid-body rotation axis.

Automated summary

We analyzed data from the Cassini spacecraft to understand the characteristics and changes of the circumglobal annuli in the stratosphere of Titan. The annuli were observed at different latitudes, with dark and bright regions. We also observed the presence of a south polar annulus, although it was not detected by the Cassini spacecraft. The stratosphere appears to rotate around the north pole or a point slightly offset from the solid-body rotation axis.