R. de Kok

Temperature and Composition of Saturn's Polar Hot Spots and Hexagon

Saturns poles exhibit an unexpected symmetry in hot, cyclonic polar vortices, despite huge seasonal differences in solar flux. The cores of both vortices are depleted in phosphine gas, probably resulting from subsidence of air into the troposphere. The warm cores are present throughout the upper troposphere and stratosphere at both poles. The thermal structure associated with the marked hexagonal polar jet at 77°N has been observed for the first time. Both the warm cyclonic belt at 79°N and the cold anticyclonic zone at 75°N exhibit the hexagonal structure.

Mapping Titan's HCN in the far infra-red: implications for photochemistry

Observations of Titans far infra-red spectra by the Cassini orbiters Composite InfraRed Spectrometer have been used to determine the latitude distribution of HCN at 1 mbar by fitting the HCN and CO rotational lines in the 18-60 cm(-1) (160-550 microm) spectral range. Results confirm the north polar HCN enrichment previously observed using mid-IR data and support the conclusion that Titans nitrile species are significantly more enriched than hydrocarbons species with similar predicted photochemical lifetimes. This suggests Titans photochemical cycle includes an additional sink for nitrogen bearing species. The abundance of CO was also determined, and had a mean value of 55 +/- 6 ppm at 20 mbar. However, it was not possible to reliably determine the CO latitude variation due to unconstrained temperatures in the north polar lower stratosphere.