Discovery of nitrogen in Saturn's inner magnetosphere

We detected N⁺ in Saturn's magnetosphere in the range L ∼ 3.5 to ∼9.5 Saturn Radii (Rs) using data collected by the Cassini Plasma Spectrometer during Saturn Orbit Insertion and the following orbit (Rev A). The presence of N⁺ in Saturn's magnetosphere has been a source of much debate since Voyager's detection of unresolved mass/charge 14-16 amu ions in this region. Two principal nitrogen sources have been suggested: Titan's atmosphere and nitrogen compounds trapped in Saturn's icy satellite surfaces (Sittler et al., 2004; E. C. Sittler et al., Energetic nitrogen ions within the inner magnetosphere of Saturn, submitted to Journal of Geophysical Research, 2004). The latter may contain primordial nitrogen, likely as NH₃ in ice (Stevenson, 1982; Squyers et al., 1983) or N⁺ that has been implanted in the surface (Delitsky and Lane, 2002). In addition to our nitrogen detection results, we also present an initial examination of possible sources of these ions.