S/2004 S 6

nowrap|S/2004 S 6 is the provisional designation of a dusty object seen orbiting Saturn very close to the F ring. It is not clear whether it is only a transient clump of dust, or if there is a solid moonlet at its core.

It was first seen by scientists in images taken by the Cassini-Huygens probe on October 28, 2004, and announced on 8 November that year. [http://cfa-www.harvard.edu/iauc/08400/08432.html IAUC 8432: "Satellites and Rings of Saturn"] 2004 November 8 (claiming recovery of nowrap|S/2004 S 3 on 17 October, 2004, in conflict with the later (2006) Spitale "et al.")] It appears to be the best tracked object in this region with at least five probable sightings in the period till late 2005. In comparison, two objects in the F ring's vicinity (nowrap|S/2004 S 3 and nowrap|S/2004 S 4) that were first seen several months earlier have not been recovered with any confidence. Nevertheless, it continues to be unclear whether there is a solid core to nowrap|S/2004 S 6 or whether it is just a transient dust clump that will dissipate on a timescale of years or months. Notably, an imaging sequence covering an entire orbital period at 4 km resolution taken on 15 November, 2004 (soon after nowrap|S/2004 S 6's discovery) failed to recover the object, while it has been seen again later. The lighting conditions in nowrap|S/2004 S 6's part of the orbit were different during these two observations, however, with the discovery being made when the region was strongly backlit by the sun. A suggested resolution of the absence in November is that nowrap|S/2004 S 6's visibility is primarily due to a diffuse cloud of fine dust that is much brighter in forward scattered light (the conditions of the discovery image), and that the solid core (if any) is small.

nowrap|S/2004 S 6 has been seen both inside and outside the main F ring, and its orbit must cross the ring. Careful calculations show that the object periodically plows through the ring material, coming within 1.5 km of the densest core e.g. on 9 April, 2005. It has been suggested that a spiral structure in the tenuous material surrounding the F ring may have been a consequence of this.cite journal | author= Charnoz, S.; "et al."| title= "Cassini Discovers a Kinematic Spiral Ring Around Saturn"| journal= Science| year= 2005| volume=310 | pages= 1300| url=http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2005Sci...310.1300C&db_key=AST&data_type=HTML&format=&high=444b66a47d06547| doi= 10.1126/science.1119387| pmid= 16311328]

The dusty halo seen in images is sizeable, being around 2000 km in lengthwise extent. The solid object, if any, would be no greater than 3−5 km in diameter based on brightness.

Additional evidence came in 2008, as it appears that S/2004 S 6 or a body like it is required to explain the dynamics of the F Ring. ["The determination of the structure of Saturn's F ring by nearby moonlets" Carl D. Murray, Kevin Beurle, Nicholas J. Cooper, Michael W. Evans, Gareth A. Williams & Sébastien Charnoz. "Nature," 5 June 2008.]

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