title: 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 x 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.
authors.affiliation: University of Colorado, Laboratory for Atmospheric and Space Physics, 234 Innovation Drive, Boulder, CO 80303-7814, USA. larry.esposito@lasp.colorado.edu
authors.forename: Larry W
authors.initials: LW
authors.lastname: Esposito
authors.forename: Joshua E
authors.initials: JE
authors.lastname: Colwell
authors.forename: Kristopher
authors.initials: K
authors.lastname: Larsen
authors.forename: William E
authors.initials: WE
authors.lastname: McClintock
authors.forename: A Ian F
authors.initials: AI
authors.lastname: Stewart
authors.forename: Janet Tew
authors.initials: JT
authors.lastname: Hallett
authors.forename: Donald E
authors.initials: DE
authors.lastname: Shemansky
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Ajello
authors.forename: Candice J
authors.initials: CJ
authors.lastname: Hansen
authors.forename: Amanda R
authors.initials: AR
authors.lastname: Hendrix
authors.forename: Robert A
authors.initials: RA
authors.lastname: West
authors.forename: H Uwe
authors.initials: HU
authors.lastname: Keller
authors.forename: Axel
authors.initials: A
authors.lastname: Korth
authors.forename: Wayne R
authors.initials: WR
authors.lastname: Pryor
authors.forename: Ralf
authors.initials: R
authors.lastname: Reulke
authors.forename: Yuk L
authors.initials: YL
authors.lastname: Yung
mesh_terms: D005118:Extraterrestrial Environment; D006859:Hydrogen; D007053:Ice; D010100:Oxygen; D018539:Saturn; D018531:Spacecraft; D013057:Spectrum Analysis; D014466:Ultraviolet Rays; D014867:Water
chemical_list: D007053:Ice; D014867:Water; D006859:Hydrogen; D010100:Oxygen