Although it appears empty from a distance, the Encke gap in Saturn's A ring has three ringlets threaded through it, two of which are visible here.
Each ringlet has dynamical structure such as the clumps seen in this image. The clumps move about and even appear and disappear, in part due to the gravitational effects of Pan.
This view looks toward the sunlit side of the rings from about 27 degrees above the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on May 11, 2013.
The view was obtained at a distance of approximately 199,000 miles (321,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 121 degrees. Image scale is 1 mile (2 kilometers) per pixel.
Saturn's rings cast shadows on the planet, except their shadows appear to be inside out! The edge of the outermost A ring can be seen at the top left corner of the image. Moving towards the bottom of the page, one can see the faint Cassini Division, the opaque B ring and the innermost C ring, which contains several ringlets that appear dark against Saturn in this geometry. The bottom half of the image features the shadows of these rings in reverse order superposed against the disk of the planet: the C ring, the B ring, the Cassini Division and the inner half of the A ring.
This view looks toward the unilluminated side of the rings from about 28 degrees below the ringplane. The image was taken with the Cassini spacecraft wide-angle camera on December 2, 2013 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 752 nanometers.
The view was acquired at a distance of approximately 750,000 miles (1.2 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 57 degrees. Image scale is 45 miles (72 kilometers) per pixel.
Zooming in on clumps in Saturn’s B-ring (lower left), the image also spans the ringlets of the Cassini Division towards the A-ring in the top right. The view looks toward the sunlit side of the rings from about 31 degrees below the ring plane. The image scale is approximately 2 km per pixel.
NASA's Cassini spacecraft has recently resumed the kind of orbits that allow for spectacular views of Saturn's rings. This view, from Cassini's imaging camera, shows the outer A ring and the F ring. The wide gap in the image is the Encke Gap, where you see not only the embedded moon Pan but also several kinky, dusty ringlets. A wavy pattern on the inner edge of the Encke gap downstream from Pan and aspiral pattern moving inwards from that edge show Pan's gravitational influence. The narrow gap close to the outer edge is the Keeler gap.
Prometheus (53 miles, or 86 kilometers across) looks like a small white bulge near the F ring -- the outermost ring seen here -- above the center of the image. See PIA08397 and PIA07712 to learn how the moon perturbs the F ring.
Kinky, discontinuous ringlets can also be seen in the Encke Gap of the A ring on the left of the image. See PIA12650 to learn more.
This view looks toward the southern, unilluminated side of the rings from about 1 degree below the ringplane. Four background stars are visible.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on January 1, 2012. The view was acquired at a distance of approximately 1.1 million miles (1.8 million kilometers) from Prometheus. Image scale is 7 miles (11 kilometers) per pixel.
Part of the Cassini Division, between the B and the A rings, appears at the top of the image, showing ringlets in the inner division.
In this image, Cassini's narrow angle camera captured a 1,200-kilometer-long (750-mile-long) section arcing along the outer edge of the B ring. Here, vertical structures tower as high as 2.5 kilometers (1.6 miles) above the plane of the rings -- a significant deviation from the vertical thickness of the main A, B and C rings, which is generally only about 10 meters (about 30 feet).
Cassiniscientists believe that this is one prominent region at the outer edge of the B ring where large bodies, or moonlets, up to a kilometer or more in size, are found. It is possible that these bodies significantly affect the ring material streaming past them and force the particles upward, in a "splashing" manner.
This image and others like it (see PIA11669) are only possible around the time of Saturn's equinox, which occurs every half-Saturn-year, or about every 15 Earthyears. The illumination geometry that accompanies equinox lowers the Sun's angle to the ring plane and causes structures jutting out of the plane to cast long shadows across the rings. The "season" of equinox allows shadows to appear on the rings in the months before and after equinox, but the actual equinox occurred August 11, 2009, as the Sun shone directly edge-on to the ring plane.
This view looks toward the southern, sunlit side of the rings from about 32 degrees below the ring plane.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 26, 2009. The view was acquired at a distance of approximately 336,000 kilometers (209,000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 132 degrees. Image scale is 2 kilometers (1 mile) per pixel.
Keeping a close watch on the outer portion of Saturn's B ring, NASA's Cassini spacecraft records the complex inward and outward movement of the edge of the ring. This ring movement resembles the suspected behavior of spiral disk galaxies.
The position of the outer edge of the B ring, shown here crossing the middle of the frame, varies with time in this concatenation of 301 images taken an average of 1 minute, 50 seconds apart, over the span of about nine hours. The total variation of the edge, from the innermost to outermost locations, is 200 kilometers (120 miles). The eccentric Huygens Ringlet, another very narrow ringlet discovered by Cassini, and the innermost of the bands of ring material in the Cassini Division, a low-density region once thought to be empty, all appear in the top of the frame.
Cassiniscientists have determined that the complicated radial variations in the B ring edge are caused by the presence of four scalloped patterns, all independently moving around the ring. One pattern, with two lobes, is present because of the gravitational perturbations from the moonMimas, which alter the ring particle orbits because of a repetitive configuration of particle and satellite orbital positions known as a Lindblad resonance; this pattern always stays fixed with respect to Mimas.
The other patterns with one, two, and three lobes respectively, travel around the ring with differing speeds and are believed to be natural modes of oscillation of the ring in this vicinity, excited by a process known as "viscous overstability." In this process, the small, random motions of the ring particles feed energy into a wave that propagates outward across the ring from an inner boundary, reflects off the outer edge of the B ring (which becomes distorted as a result), and then travels inward until it reflects off the inner boundary. This continuous back-and-forth reflection is necessary for these wave patterns to grow and become visible as distortions in the outer edge of the B ring.
In supporting these so-called "self-excited" modes, the outer edge of the B ring is behaving the way astronomers believe spiral galaxies behave. However, such modes are not directly observable in galaxies. Cassini's observations of the outer B ring edge constitute the first time such large-scale modes in a broad disk of material have been observed in nature.
The movie repeats twice. The second time the movie runs, the location of the Mimas resonance (marked with a green line), the locations of the inner boundaries for the one-lobed (blue), two-lobed (yellow), and three-lobed (red) modes, and the location of the mean radius of the outer edge of the B ring (white) are all indicated.
The images were re-projected into the same viewing geometry and magnified by a factor of two to increase visibility of features. Image scale was about 2 kilometers (about 1 mile) per pixel in the original images. These images have not been cleaned of cosmic rays that struck the camera's sensor during exposure. These cosmic ray hits appear as small white streaks on the images.
The view looks toward the southern, sunlit side of the rings from about 44 degrees below the ring plane.
The images were taken in visible light with the Cassini spacecraft narrow-angle camera on January 28, 2008. The view was acquired at a distance of approximately 424,000 kilometers (264,000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 52 degrees.
Structure is clearly visible in the ringlets that occupy the Encke Gap in the lower right of this image. A peculiar kink can be seen in one particularly bright ringlet at the bottom right. To view vertical structures in these kinky, discontinuous ringlets casting shadows during Saturn's August 2009 equinox, see PIA11676.
Nearly uniform striations in the A ring created by the gravitational effects of the moonPan dominate the left of this image. Saturn is out of the frame to the right. Also visible are two waves -- darker banded structures -- to the left of the Encke gap. See PIA10501 to learn more about the waves present here.
This view looks toward the southern, unilluminated side of the rings from about 18 degrees below the ringplane.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on June 3, 2010. The view was acquired at a distance of approximately 177,000 kilometers (110,000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 60 degrees. Image scale is 700 meters (2,296 feet) per pixel.
The moonPan (28 kilometers, or 17 miles across) casts a long shadow towards the right from where it orbits in the Encke Gap of the A ring in the upper right of the image. A structure in the thin F ring casts a short shadow on that ring in the upper left of the image. Kinky ringlets in the Encke Gap also cast many shadows in the middle and lower portions of the image, but some of those shadows appear faint.
The novel illumination geometry that accompanies equinox lowers the Sun's angle to the ringplane, significantly darkens the rings, and causes out-of-plane structures to look anomalously bright and cast shadows across the rings. These scenes are possible only during the few months before and after Saturn's equinox, which occurs only once in about 15 Earthyears. Before and after equinox, Cassini's cameras have spotted not only the predictable shadows of some of Saturn's moons (see PIA11657), but also the shadows of newly revealed vertical structures in the rings themselves (see PIA11665).
This view looks toward the northern, sunlit side of the rings from about 11 degrees above the ringplane.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on August 19, 2009. The view was acquired at a distance of approximately 2.3 million kilometers (1.4 million miles) from Saturn. Image scale is 13 kilometers (8 miles) per pixel.
Saturn's small, ring-embedded moonPan, on the extreme right of this Cassini spacecraft image, can be seen interacting with the ringlets that share the Encke Gap of the A ring with this moon.
Pan is 28 kilometers, or 17 miles, across. This view looks toward the northern, sunlit side of the rings from about 11 degrees above the ringplane.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on June 2, 2010. The view was acquired at a distance of approximately 875,000 kilometers (544,000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 130 degrees. Image scale is 5 kilometers (3 miles) per pixel.
