Where has all the Nitrogen Gone?

Titan possesses a high density atmosphere consisting primarily of molecular nitrogen. It has been, for decades, the general expectation that there should be a torus of neutral and ionized nitrogen associated with Titan and a considerable body of literature on the nature of this putative nitrogen atmosphere exists. Hot pickup nitrogen ions would not have been observable by means of the PLS instrument on Voyager, but the cases of cold ions that were detected outside the main plasma body of Saturn exhibited a degree of statistical preference for identification as water group ions. The CAPS experiment on Cassini which has mass identification capability has found that the plasma existing in the volume of space expected to contain the anticipated nitrogen torus is dominated by water group components. In this study we consider the modes of escape of nitrogen from Saturn and the loss mechanisms that appear to preclude the formation of the dense plasma and neutral torus that had been anticipated in the wake of the Voyager findings. We assess models that predict the escape of Titan atmosphere components including nitrogen and various hydrocarbons. We also evaluate the extent to which Titan might constitute as minor contributor to the population of nitrogen ions that has been observed by CAPS in the domain of the inner icy satellites.