Ultraviolet Imaging Spectroscopy Shows an Active Saturnian System

Abstract

Neutral oxygen in the saturnian system shows variability, and the total number of oxygen atoms peaks at 4 × 10 34 . Saturn's aurora brightens in response to solar-wind forcing, and the auroral spectrum resembles Jupiter's. Phoebe's surface shows variable water-ice content, and the data indicate it originated in the outer solar system. Saturn's rings also show variable water abundance, with the purest ice in the outermost A ring. This radial variation is consistent with initially pure water ice bombarded by meteors, but smaller radial structures may indicate collisional transport and recent renewal events in the past 10 7 to 10 8 years.