Characteristics of Titanʹs stratospheric aerosols and condensate clouds from Cassini CIRS far-infrared spectra

Four broad spectral features were identified in far-infrared limb spectra from the Cassini Composite Infrared Spectrometer (CIRS), two of which have not been identified before. The features are broader than the spectral resolution, which suggests that they are caused by particulates in Titanʹs stratosphere. We derive here the spectral properties and variations with altitude for these four features for six latitudes between 65° S and 85° N. Titanʹs main aerosol is called Haze 0 here. It is present at all wavenumbers in the far-infrared and is found to have a fractional scale height (i.e., the aerosol density scale height divided by the atmospheric density scale height) between 1.5 and 1.7 with a small increase in opacity in the north. A second feature around 140 cm−1 (Haze A) has similar spatial properties to Haze 0, but has a smaller fractional scale height of 1.2–1.3. Both Haze 0 and Haze A show an increase in retrieved abundance below 100 km. Two other features (Haze B around 220 cm−1 and Haze C around 190 cm−1) have a large maximum in their density profiles at 140 and 90 km, respectively. Haze B is much more abundant in the northern hemisphere compared to the southern hemisphere. Haze C also shows a large increase towards the north, but then disappears at 85° N.