This mosaic of images from NASA's Cassini spacecraft shows three fan-like structures in Saturn's tenuous F ring. Such "fans" suggest the existence of additional objects in the F ring.
From right to left in the mosaic, each fan appears dark above the bright core of the F ring near the larger, diagonal channels created by the ring's shepherding moon Prometheus. The fans (marked "F" in the annotated version) can be seen developing as a series of channels within the F ring's particles. They appear to have a common origin but spread outward radially in different directions. Gravitational perturbations on 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. It is probably embedded in the ring and causing the base of the fan channels to meet. See PIA12785 and 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, or 92 miles, on its longest side but is on average 86 kilometers, or 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 10 images was taken over the span of about one hour, 14 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 6 kilometers (4 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 26 degrees above the ring plane.
The images were taken in visible light with the Cassini spacecraft narrow-angle camera on July 5, 2008. The view was acquired at a distance of approximately 1.1 million kilometers (684,000 miles) from Saturn and at a sun-Saturn-spacecraft, or phase, angle of 34 degrees.
The Cassini Equinox Mission is a joint United States and European endeavor. 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 was designed, developed and assembled at JPL. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.