36th DPS Meeting, 8-12 November 2004
Session 4 Phoebe and Iapetus
Oral, Monday, November 8, 2004, 1:30-3:00pm, Lewis

[Previous] | [Session 4] | [Next]

[4.05] Ultraviolet Observations of Phoebe and Iapetus from Cassini

A.R. Hendrix, C.J. Hansen (JPL/Caltech), L.W. Esposito (LASP/CU), D.E. Shemansky (USC), J.E. Colwell (LASP/CU)

We present results from the Ultraviolet Imaging Spectrograph (UVIS) measurements of Phoebe during the Cassini flyby on June 11, 2004. Cassini UVIS mapped the illuminated side of Phoebe at resolutions on the order of 5-10 km/pixel. Phoebe is known to be dark and spectrally flat at all visible wavelengths, similar to C-type asteroids. Unresolved Earth-based observations have detected the presence of water ice. We find that the normal albedo of Phoebe is very low (<0.05) at far-UV wavelengths (110-190 nm), similar to carbonaceous chondrites. Phoebe's FUV spectral albedo, however, is not flat like such meteorites, suggesting that another species strongly affects the FUV spectrum. We investigate candidate species, and study albedo and spectral variations across the surface, to map distributions of species. We also present Phoebe's UV lightcurve, measured during both the inbound and outbound portions of the flyby. In addition to the reflectance studies we investigate the presence of any emissions from gaseous species. Phoebe's spectrum does not display any strong emission features, suggesting that gaseous species are not present and/or that the density of solar wind electrons in Phoebe's environment is too low to produce excitation emission features. We also report on the disk-integrated observations of Iapetus throughout October, 2004, at ranges between 1 and 2 million km. The FUV spectra of Iapetus will be compared with the Phoebe data to investigate a possible relationship between these two satellites .

[Previous] | [Session 4] | [Next]

Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.