Cassini CAPS-ELS Observations of Negative Ions in Titan's Ionosphere: Solar Zenith Angle - Density Trends
- 1University College London, Mullard Space Science Laboratory, UK
- 2The Centre for Planetary Sciences at UCL/Birkbeck, UK
- 3Swedish Institute of Space Physics, Uppsala, Sweden
- 4Group de Spectrométrie Moléculaire et Atmosphérique, Université de Reims, France
- 5Institut de Planétologie et d'Astrophysique de Grenoble, France
The discovery of heavy organic anions by in situ measurements using Cassini’s CAPS Electron Spectrometer (ELS) in Titan’s ionosphere was an unexpected result of the Cassini mission (Coates et al, 2007, Waite et al, 2007); a complete reconsideration of chemical processes in this enigmatic atmosphere was necessary as a result. These negative ions can be associated with complex hydrocarbon and nitrile processes which are linked to haze formation at lower altitudes. Cassini’s CAPS ELS observed negative ions during Titan encounters at altitudes below 1400 km. The ions can reach masses over 13,000 amu/q (Coates et al., 2009), while recurring peaks in the mass spectra can be used to identify different mass groups as reported by Coates et al. (2007) and Wellbrock et al. (2013, 2019). Studying density and mass trends of these groups helps to identify controlling factors of the production and destruction mechanisms, and ultimately to improve our understanding of how organic macromolecules can be produced by naturally occurring abiotic processes. In this study we examine the effects different solar zenith angle conditions might have on both the light and heavy negative ion mass groups, and consider the role of processes such as photodetachment and dissociative electron attachment. We also compare the negative ion data with RPWS electron measurements and discuss the possible implications associated with the above processes.
How to cite: Wellbrock, A., Coates, A., Jones, G., Haythornthwaite, R., Shebanits, O., Vigren, E., Lavvas, P., and Vuitton, V.: Cassini CAPS-ELS Observations of Negative Ions in Titan's Ionosphere: Solar Zenith Angle - Density Trends, European Planetary Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-778, https://doi.org/10.5194/epsc2021-778, 2021.