Observations of molecular oxygen ions in Saturn's inner magnetosphere

[1] We present an analysis of molecular oxygen ion (O2+) abundance in Saturn's inner magnetosphere based on observations made with the Cassini Plasma Spectrometer (CAPS). Using data summed over 23 orbits, we resolve and isolate O2+ counts from the tail of the water group ion mass distribution (W+ [O+, OH+, H2O+, H3O+]) and from background sources. O2+ was initially estimated at ∼1–2% of the total ion population in the inner magnetosphere based on CAPS data from the Saturn orbital insertion pass. Through refined analysis techniques, we have found O2+ to account for just above 0.3% of all W+ ions at L = 4.5, with only minor fluctuations in relative density out to L = 7.5 − 8.0. Beyond L = 7.5, the relative O2+/W+ abundance exhibits a statistically significant increase through L = 10.5, which may indicate a neutral O2 source in the vicinity of Rhea.