Heavy Positive Ion Groups in Titan’s Ionosphere from Cassini Plasma Spectrometer IBS Observations

Titan's ionosphere contains a plethora of hydrocarbons and nitrile cations anions as measured by the Ion Neutral Mass Spectrometer Cassini Plasma (CAPS) onboard spacecraft. Data from CAPS Beam (IBS) sensor have been examined for five close encounters Titan during 2009. The high relative velocity with respect to cold ions in allows IBS function mass spectrometer. Positive ion masses between 170 310 u/q are groups identified 275 containing 14 21 heavy (carbon/nitrogen/oxygen) atoms. These heaviest positive reported so far available situ data at Titan. group peaks found be consistent associated Polycyclic Aromatic Compounds (PAC), including Hydrocarbon (PAH) nitrogen-bearing polycyclic aromatic molecular ions. peak identifications compared previously proposed neutral PAHs similar masses, supporting PAH interpretation. spacing is also investigated, finding 12 or 13 indicating addition C CH. Lastly, occurrence several seen vary across flybys studied, possibly relating varying solar radiation conditions observed flybys. findings further understanding low negative ions, well aerosol formation atmosphere.