|Annotated Version||Â||Cropped Inset|
Bright clumps of ring material and a fan-like structure appear near the core of Saturn's tenuous F ring in this mosaic of images from NASA's Cassini spacecraft. Such features suggest the existence of additional objects in the F ring.
These discontinuous clumps near the core of the F ring may be created by the passage of the ring's shepherding moon Prometheus, and they can be seen casting narrow shadows that extend toward the bottom of the mosaic. The shadows are marked with arrows in the annotated version. On the right of the mosaic, a "fan" can be seen dissipating above the bright ring core. The fan (marked "F" in the annotated version) is a series of channels within the F ring's particles that appear to have a common origin but that spread outward radially in different directions. Gravitational perturbations on the ring material by a moonlet or clump of material can create these fans. The moonlet or clump orbits more or less elliptically compared to the rest of the F ring can create these fans. It is probably embedded in the ring and is causing the base of the fan channels to meet. See PIA12786 for similar observations of such fans.
The diagonal streamer-channels are periodically created by the gravity of the potato-shaped moon Prometheus which is 148 kilometers (92 miles) on its longest side but is on average 86 kilometers (53 miles) across. To learn more and to watch a movie of this streamer-channel phenomenon, see PIA08397.
The images have been re-projected in this mosaic so that the F ring appears straightened rather than curved and compressed azimuthally (along the ring). This change represents a scale compression in the horizontal direction of about 33 to one which is why Prometheus looks like a bright line. Prometheus is marked "Pr" in the annotated version.
This sequence of 42 images was taken over a span of one hour, seven minutes. The earliest image is on the right, and time progresses moving left in the mosaic. Each image was cropped, re-projected and placed side by side in this montage. Scale in the original images was about 3 kilometers (2 miles) per pixel. The images were contrast enhanced and re-projected to a scale of 33 kilometers (21 miles) per pixel in the mosaic's horizontal direction and one kilometer (0.6 miles) per pixel in the mosaic's vertical direction. The single, cropped inset of the clumps included here was then magnified by a factor of two.
The view in the original images looked toward the northern, unilluminated side of the rings from about 70 degrees above the ring plane.
The images were taken in visible light with the Cassini spacecraft narrow-angle camera on Dec. 8, 2008. The view was obtained at a range of distances from approximately 597,000 kilometers (371,000 miles) to 615,000 kilometers (382,000 miles) from Saturn and at a sun-Saturn-spacecraft, or phase, angle of 77 degrees.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.