Epimetheus, Janus, Pandora and Prometheus Amid the Rings

Two pairs of moons make a rare joint appearance. The F ring's shepherd moons, Prometheus and Pandora, appear just inside and outside of the F ring (the thin faint ring furthest from Saturn). Meanwhile, farther from Saturn the co-orbital moons Janus (near the bottom) and Epimetheus (about a third of the way down from the top) also are captured.

Prometheus (53 miles, or 86 kilometers across) and Pandora (50 miles, or 81 kilometers across) sculpt the F ring through their gravitational influences. Janus (111 miles, or 179 kilometers across) and Epimetheus (70 miles, or 113 kilometers across) are famous for their orbital dance, swapping places about every four years. They are also responsible for gravitationally shaping the outer edge of the A ring into seven scallops.

This view looks toward the sunlit side of the rings from about 47 degrees above the ringplane. The image was taken in visible light with the Cassini spacecraft wide-angle camera on October 11, 2013.

The view was acquired at a distance of approximately 810,000 miles (1.3 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 47 degrees. Image scale is 47 miles (76 kilometers) per pixel.

Photo credit: NASA/JPL-Caltech/Space Science Institute

Crescent Saturn

Saturn, which appears as only a thin, lit crescent, broken only by the shadows of its rings, poses gracefully for the Cassini spacecraft cameras.

This view looks toward the unilluminated side of the rings from about 42 degrees below the ringplane. The image was taken with the Cassini spacecraft wide-angle camera on September 20, 2013 using a spectral filter which only admits wavelengths of near-infrared light centered at 752 nanometers.

The view was obtained at a distance of approximately 1.4 million miles (2.3 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 142 degrees. Image scale is 84.5 miles (136 kilometers) per pixel.

Photo credit: NASA/JPL-Caltech/Space Science Institute

Rhea

A nearly full Rhea shines in the sunlight in this recent Cassini image.

Rhea (949 miles, or 1,527 kilometers across) is Saturn's second largest moon.

Lit terrain seen here is on the Saturn-facing hemisphere of Rhea. North on Rhea is up and rotated 43 degrees to the left. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on September 10, 2013.

The view was obtained at a distance of approximately 990,000 miles (1.6 million kilometers) from Rhea. Image scale is 6 miles (9 kilometers) per pixel.

Photo credit: NASA/JPL-Caltech/Space Science Institute

Titan's Internal Structure

This artist’s concept shows a possible model of Titan’s internal structure that incorporates data from NASA’s Cassini spacecraft. In this model, Titan is fully differentiated, which means the denser core of the moon has separated from its outer parts. This model proposes a core consisting entirely of water-bearing rocks and a subsurface ocean of liquid water. The mantle, in this image, is made of icy layers, one that is a layer of high-pressure ice closer to the core and an outer ice shell on top of the sub-surface ocean.

A model of Cassini is shown making a targeted flyby over Titan’s cloudtops, with Saturn and Enceladus appearing at upper right.

The model, developed by Dominic Fortes of University College London, England, incorporates data from Cassini’s radio science experiment.

Image credit: A. D. Fortes/UCL/STFC

Note: For more information, see Cassini Nears 100th Titan Flyby with a Look Back.

Ring Spokes and Mimas

Among the interplay of Saturn's shadow and rings, Mimas, which appears in the lower-right corner of the image, orbits Saturn as a set of the ever-intriguing spokes appear in the B ring (just to the right of center).

Scientists expect that spokes will soon cease to form as Saturn approaches northern equinox. The exact mechanism of spoke formation is still the subject of debate, but ring scientists do know that spokes no longer appear when the Sun is higher in Saturn's sky. It is believed that this has to do with the ability of micron-sized ring grains to maintain an electrical charge and levitate above the rings, forming spokes. Thus, these may be some of the last spokes ever imaged by Cassini.

This view looks toward the unilluminated side of the rings from about 38 degrees below the ringplane. The image was taken in visible light with the Cassini spacecraft wide-angle camera on October 22, 2013.

The view was obtained at a distance of approximately 1.6 million miles (2.6 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 146 degrees. Image scale is 93 miles (150 kilometers) per pixel.

Photo credit: NASA/JPL-Caltech/Space Science Institute

Saturn's D-Ring

Saturn's D ring is easy to overlook since it's trapped between the brighter C ring and the planet itself. But this dusty ring has plenty to teach us. In this view, all that can be seen of the D ring is the faint and narrow arc as it stretches from top right of the image.

If all goes as planned, Cassini will pass between the D ring and Saturn in its final orbits in 2017. Scientists expect to gather unprecedented data from these orbits.

Also visible in this image are 12 stars.

This view looks toward the unilluminated side of the rings from about 41 degrees below the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on October 21, 2013.

The view was obtained at a distance of approximately 1.5 million miles (2.4 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 140 degrees. Image scale is 8.7 miles (14 kilometers) per pixel.

Photo credit: NASA/JPL-Caltech/Space Science Institute

Dione

Although the crack-like features seen here on Dione surface appear wispy and faded, they are in reality a series of geologically fresh fractures!

See PIA10560 to learn more about Dione's wispy terrain.

Lit terrain seen here is on the trailing hemisphere of Dione. North on Dione (698 miles, or 1,123 kilometers across) is up and rotated 29 degrees to the left. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on September 10, 2013.

The view was acquired at a distance of approximately 554,000 miles (892,000 kilometers) from Dione. Image scale is three miles (five kilometers) per pixel.

Photo credit: NASA/JPL-Caltech/Space Science Institute

Saturn's Auroras

Ultraviolet and infrared images from NASA's Cassini spacecraft and Hubble Space Telescope show active and quiet auroras at Saturn's north and south poles.

Saturn's auroras glow when energetic electrons dive into the planet's atmosphere and collide with hydrogen molecules. Sometimes a blast of fast solar wind, composed of mostly electrons and protons, creates an active aurora at Saturn, as occurred on April 5 and May 20, 2013.

The first set of images, as seen in the ultraviolet part of the spectrum by Hubble, shows an active aurora dancing around Saturn's north pole on April 5. The movie then shows a relatively quiet time between April 19 to 22 and between May 18 and 19. The aurora flares up again in Hubble images from May 20. This version, shown in false-color, has been processed to show the auroras more clearly.

A second set of ultraviolet images shows a closer view of an active north polar aurora in white. This set comes from Cassini ultraviolet imaging spectrograph observations on May 20 and 21.

The last set of images, in the infrared, shows a quiet southern aurora (in green) in observations from Cassini's visual and infrared mapping spectrometer on May 17. Saturn's inner heat glows in red, with dark areas showing where high clouds block the heat.

Video credit: NASA/JPL-Caltech/University of Colorado/Central Arizona College and NASA/ESA/University of Leicester and NASA/JPL-Caltech/University of Arizona/Lancaster University

Note: For more information, see PIA17668: Saturn's Colorful Aurora, NASA Spacecraft Get a 360-Degree View of Saturn's Auroras and PIA17669: Pulses from the Sun.

F-Ring Strand

Saturn's F ring often appears to do things other rings don't. In this Cassini spacecraft image, a strand of ring appears to separate from the core of the ring as if pulled apart by mysterious forces.

Some ring scientists believe that this feature may be due to repeated collisions between the F ring and a single small object.

Eight stars are also visible in this image.

This view looks toward the unilluminated side of the rings from about 49 degrees below the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on October 19, 2013.

The view was obtained at a distance of approximately 1.2 million miles (1.9 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 120 degrees. Image scale is 6.8 miles (11 kilometers) per pixel.

Photo credit: NASA/JPL-Caltech/Space Science Institute

Saturn's Northern Hemisphere Storm, 6 March 2011

Like a swirl from a paintbrush being dipped in water, this image from the Cassini orbiter shows the progress of a massive storm on Saturn. The storm first developed in December 2010, and this mosaic captures how it appeared on 6 March 2011.

The head of the storm is towards the left of the image, where the most turbulent activity is shown in white, but towards the center you can also see the trace of a spinning vortex in the wake of the storm.

This image, centered at about 0º longitude and 35º N latitude, has had its colors enhanced to help reveal the complex processes in Saturn’s weather. The white corresponds to the highest cloud tops, but to the human eye the storm would appear more as a bright area against a yellow background.

Cassini also monitored the temperature of the storm, showing a rapid spike as energy was released into the atmosphere.

The storm grew so large that on Earth it would easily cover all of Europe. Atmospheric disturbances of this size can be expected once during each of Saturn’s orbits around the Sun, which takes 30 Earth years. However, this particular event surprised scientists by occurring during the northern hemisphere spring, rather than the more typically stormy Saturnian summer.

Image credit: NASA/JPL-Caltech/SSI/Hampton University