Integrated Laboratory, Modeling and Observational Investigations of the Condensation of Benzene on Titan's Stratospheric Aerosols
Abstract
Aerosols in Titan's atmosphere play an important role in determining its thermal structure and can act as condensation nuclei for the formation of clouds. The global circulation of Titan's atmosphere reversed within the two years following the northern spring equinox in August 2009, increasing the mixing ratios of benzene (C6H6) and other species at the South pole. A simultaneous strong cooling above the south pole (dropping temperatures below 120 K) resulted in conditions where molecules could condense at unusually high altitudes (>250 km). C6H6 and HCN ices have been detected by the Composite Infrared Spectrometer (CIRS) and the Visible and Infrared Mapping Spectrometer (VIMS), respectively, in the South polar cloud system, but the existing laboratory data is insufficient to allow models to reproduce the formation of the observed cloud system. We will present the preliminary results and the overall scope of a newly funded NASA SMD Cassini Data Analysis Program (CDAP) project which proposes to combine laboratory, modeling and observational studies to investigate the condensation of benzene on Titan's aerosol as an important component of the cloud system that appeared during the autumn at 300 km above Titan's South pole. The project goals are: 1) (lab) to measure the vapor pressure of benzene at Titan-relevant temperatures using the Ames Atmospheric Chemistry Laboratory[1], 2) (lab) to produce analogs of Titan's aerosols using the Titan Haze Simulation experiment developed on the NASA Ames COSmIC facility[2] and investigate the conditions required for condensation of benzene on them using the ACL, 3) (model) to use the experimental data to constrain nucleation and condensation in microphysical models[3], in order to determine expected cloud altitudes and particle sizes, and 4) (observation) to compare our experimental data and modeling output with observations from CIRS in the 9-17 µm spectral region[4], in order to better understand the molecular composition of this cloud system. References: [1] Iraci, L. T. et al., Icarus 210(2), 985-991, 2010. [2] Sciamma-O'Brien, E. et al., Icarus 289, 214-226, 2017. [3] Barth E. L., Planet. Space Sci. 127, 20-31, 2017. [4] Vinatier, S. et al., Icarus 310, 89-104, 2018.
- Publication:
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AAS/Division for Planetary Sciences Meeting Abstracts #50
- Pub Date:
- October 2018
- Bibcode:
- 2018DPS....5022111S