2013 Annual Science Report
NASA Jet Propulsion Laboratory - Titan Reporting | SEP 2012 – AUG 2013
Task 126.96.36.199: Titan Photochemistry
The Caltech effort has focused on the chemistry of hydrocarbons in the atmosphere of Titan and its relation to aerosols. We have an effort for analyzing the stellar occultation data from Cassini/UVIS instrument. The mean optical depth as a function of line of sight impact parameter is derived for the spectral range between 1700 and 1900 Å from stellar occultations.
Vertical profiles of tholin particles above ~300 km are retrieved. The profiles show two depletion regions: 750-800 km and 400-500 km ranges. A photochemistry-transport is developed and used to interpret the production, loss, and transport in the atmosphere. Processes that affect the profile are (1) aerosol production via ion-neutral and neutral-neutral chemical reactions, (2) aggregation to form fractal aggregates, (3) aerosol coagulation, and (4) diffusion and dynamical transport via gravitational settling. Sensitivity of the resulting tholin profile to the above processes is examined.