New Epimetheus Image: Epimetheus on the Outside

CICLOPS released yesterday this view of Epimetheus taken from a distance of 1.8 million km on June 30. In this image, you can't seem much detail on Epimetheus from this distance but faint features within the outer A ring and the F ring are clearly visible.

Icarus (September 2005)

The index for the September issue of Icarus is now online. Icarus is the journal for the American Astronomical Society's Division of Planetary Science. A number of outer satellite papers are in this issue:

• Thermal response of Iapetus to an eclipse by Saturn's rings by G. Neugebauer, K. Matthews, P.D. Nicholson, B.T. Soifer, I. Gatley and S.V.W. Beckwith
• The Zamama–Thor region of Io: Insights from a synthesis of mapping, topography, and Galileo spacecraft data by David A. Williams, Laszlo P. Keszthelyi, Paul M. Schenk, Moses P. Milazzo, Rosaly M.C. Lopes, Julie A. Rathbun and Ronald Greeley
• Maps of Titan's surface from 1 to 2.5 μm by Athena Coustenis, Mathieu Hirtzig, Eric Gendron, Pierre Drossart, Olivier Lai, Michel Combes and Alberto Negrão
• Photochemical processes on Titan: Irradiation of mixtures of gases that simulate Titan's atmosphere by Buu N. Tran, Jeffrey C. Joseph, Michael Force, Robert G. Briggs, Veronique Vuitton and James P. Ferris
• Condensed species in Titan's atmosphere: Identification of crystalline propionitrile (C₂H₅CN, CH₃CH₂CN) based on laboratory infrared data by R.K. Khanna

The paper by Williams et al. is a good one. It gives a great description of the 2001 eruption at Thor.

Naming Categories on Titan

The IAU has approved several changes to the nomenclature of Titan. No names are available (yet), but several changes are encouraging. First, the faculas will be named after islands on Earth (not politically independent). Faculae (groups of bright features) will be named after archipelagoes on Earth. Secondly, a new category has been approved, Flumina. These are channels on Titan that MAY carry liquid. They will be named after mythical or imaginary rivers.

The "categories" page was last updated July 5 so this kinda of old news but this is the first I have seen some of these changes on the web.

Raw Images of the Day

It's time now for Raw images of the Day:

• Prometheus, Epimetheus, and Janus in the same shot
• Tirawa, South Tirawa Basin, and the ray crater on Rhea
• Nice view of Janus
• Ithaca Chasma on Tethys
• Cassini Regio on Iapetus

Mimas map

Steve Albers has a new version of his Mimas map on his website. The map includes data from Voyager and Cassini, including last week's encounter. Certainly a lot better than the maps available else where on the web. The map includes improved coverage over Herschel as well as in the anti-Saturnian hemisphere.

Also, don't forget to check out the improved Enceladus map, that now includes data from last month's flyby.

Enceladus, plumes, and the CDA

Bruce Moomaw has a pretty length post over at the Unmanned Spaceflight.com forum covering some confusion regarding the Cosmic Dust Analyzer (CDA) results from the Enceladus flyby last month. The confusion results from whether the particles seen by the CDA instrument were in fact from impact-generated dust, or from a south polar plume. Early analysis suggested that the particles came from impact-generated dust rather than the south polar "plume" since the dust appeared to be uniform over the surface while the atmosphere/plume is not. Emily Lakdawalla, from the Planetary Society, posted an article a week or so ago describing the results, using information from the press release and an interview with Linda Spilker, the Cassini Deputy Project Scientist. In the article, Lakdawalla quoted Spilker as saying that the dust seen by the CDA instrument (the dust near Enceladus and the E-ring) were different from the water vapor seen by UVIS, INMS, and MAG, and that the south polar vents were not the source of the E-ring. However, as Bruce mentioned in a comment here, if the E-ring was generated solely by impacts on Enceladus, wouldn't other moons like Mimas have the same sort of impact-generated ring co-orbiting with the satellite.. So Bruce did a little digging and talked with Spilker. Turns out that Lakdawalla quoted her incorrectly. The difference between the CDA dust and the atmosphere seen by UVIS et al. is that the CDA saw water particles and UVIS et al. saw water vapor, nothing more.

In addition, Bruce dug up a new tidbit. Previously, the CDA team has been reporting that the dust was uniform across the surface (leading to the conclusion that the particles didn't have a localized source). Even if the particles were formed by condensing water vapor from the vent, there would be some sort of asymmetry in the CDA data biased to the south polar region. Turns out that the CDA may have seen an asymmetry in the amount of dust with respect to location over Enceladus. This is a very intriguing development and may indicate that the particles near Enceladus and perhaps the E-ring itself were formed from condensing particles from vents in the south polar region.

Raw Images of the Week

Quite news day today, Cassini-wise. So here are some raw images:

• Half-phase Rhea
• Eastern Cassini Region on Iapetus
• Wispy terrain on Dione
• Penelope crater on Tethys
• Looking back at Mimas
• Impact basins coming into view on Rhea
• Two-tone Tethys
• Featureless Enceladus