The organic aerosols of Titan’s atmosphere

• Main Authors: Sotin, Christophe, Lawrence, Kenneth, Beauchamp, Patricia M., Zimmerman, Wayne
• Format: Report
• Language: English
• Published: Pasadena, CA : Jet Propulsion Laboratory, National Aeronautics and Space Administration, 2012. 2013
• Subjects: Titan; organic molecules; atmosphere; solar occultation; Instrumentation and Photography; South Pole; South pole
• Online Access: http://hdl.handle.net/2014/43184

One of Titan's many characteristics is the presence of a haze that veils its surface. This haze is composed of heavy organic particles and determining the chemical composition of these particles is a primary objective for future probes that would conduct in situ analysis. Meanwhile, solar occultations provide constraints on the optical characteristics of the haze layer. This paper describes solar occultation observations obtained by the Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft. These observations strongly constrain the optical characteristics of the haze layer. We detail the different steps involved in the processing of these data and apply them to two occultations that were observed at the South Pole and at the equator in order to investigate the latitudinal dependence of optical properties. The light curves obtained in seven atmospheric windows between 0.933-μm to 5-μm allow us to characterize atmospheric layers from 300 km to the surface. Very good fits of the light curves are obtained using a simple profile of number density of aerosols that is characterized by a scale height. The main difference between the South Pole and the equator is that the value of the scale height increases with altitude at the South Pole whereas it decreases at the equator. The vertically integrated amount of aerosols is similar at the two locations. The curve describing the cross-section versus wavelength is identical at the two locations suggesting that the aerosols have similar characteristics. Finally, we find that the two-way vertical transmission at 5-μm is as large as 80% at both locations. NASA/JPL