Mimas and Ring Shadow

As if trying to get our attention, Mimas is positioned against the shadow of Saturn's rings, bright on dark. As we near summer in Saturn's northern hemisphere, the rings cast ever larger shadows on the planet.

With a reflectivity of about 96 percent, Mimas (246 miles, or 396 kilometers across) appears bright against the less-reflective Saturn.

This view looks toward the sunlit side of the rings from about 10 degrees above the ringplane. The image was taken with the Cassini spacecraft wide-angle camera on July 13, 2014 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 1.1 million miles (1.8 million kilometers) from Saturn and approximately 1 million miles (1.6 million kilometers) from Mimas. Image scale is 67 miles (108 kilometers) per pixel at Saturn and 60 miles (97 kilometers) per pixel at Mimas.

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

Two Ringlets in the Encke Gap

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.

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

Saturn From Above

Saturn reigns supreme, encircled by its retinue of rings.

Although all four giant planets have ring systems, Saturn's is by far the most massive and impressive. Scientists are trying to understand why by studying how the rings have formed and how they have evolved over time.

Also seen in this image is Saturn's famous north polar vortex and hexagon.

This view looks toward the sunlit side of the rings from about 37 degrees above the ringplane. The image was taken with the Cassini spacecraft wide-angle camera on May 4, 2014 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 2 million miles (3 million kilometers) from Saturn. Image scale is 110 miles (180 kilometers) per pixel.

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

Note: For more information, see Supreme Saturn.

Rhea and Epimetheus

Saturn has a great many more moons than our planet – a whopping 62. A single moon, Titan, accounts for an overwhelming 96% of all the material orbit the planet, with a group of six other smaller moons dominating the rest. The other 55 small satellites whizzing around Saturn make up the tiny remainder along with the gas giant’s famous rings.

One of the subjects of this Cassini image, Rhea, belongs to that group of six. Set against a backdrop showing Saturn and its intricate system of icy rings, Rhea dominates the scene and dwarfs its tiny companion, one of the 55 small satellites known as Epimetheus.

Although they appear to be close to one another, this is a trick of perspective – this view was obtained when Cassini was some 1.2 million km from Rhea, and 1.6 million km from Epimetheus, meaning the moons themselves had a hefty separation of 400,000 km.

However, even if they were nearer to each other, Rhea would still loom large over Epimetheus: at 1528 km across and just under half the size of our own Moon, Rhea is well over 10 times the size of Epimetheus, which is a modest 113 km across.

As is traditional for the earliest discovered moons of Saturn, both are named after figures from Greek mythology: the Titan Rhea (“mother of the gods”) and Prometheus’ brother Epimetheus (“after thinker” or “hindsight”).

This image was taken by Cassini’s narrow-angle camera on 24 March 2010. A monochrome version was previously released by NASA as PIA12638: Big and Small Before Rings.

Image credit: Image data credit: NASA/JPL-Caltech/Space Science Institute; Processed image copyright: G. Ugarković

Pandora and the Rings

The F ring shepherd Pandora is captured here along with other well-known examples of how Saturn’s moons shape the rings. From the narrow F ring, to the gaps in the A ring, to the Cassini Division, Saturn's rings are a masterpiece of gravitational sculpting by the moons.

Pandora (50 miles, or 81 kilometers across), along with its fellow shepherd Prometheus (53 miles, or 86 kilometers across), helps confine the F ring and keep it from spreading.

This view looks toward the unilluminated side of the rings from about 31 degrees below the ringplane. The image was taken in visible light with the Cassini spacecraft wide-angle camera on March 8, 2014.

The view was obtained at a distance of approximately 533,000 miles (858,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 63 degrees. Image scale is 32 miles (51 kilometers) per pixel.

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

Note: For more information, see Shepherd and Flock.

Prometheus and the Rings

Seen within the vast expanse of Saturn's rings, Prometheus appears as little more than a dot. But that little moon still manages to shape the F ring, confining it to its narrow domain.

Prometheus (53 miles, or 86 kilometers across) and its fellow moon Pandora (50 miles, or 81 kilometers across) orbit beside the F ring and keep the ring from spreading outward through a process dubbed "shepherding."

This view looks toward the unilluminated side of the rings from about 45 degrees below the ringplane. The image was taken in green light with the Cassini spacecraft wide-angle camera on March 8, 2014.

The view was obtained at a distance of approximately 533,000 miles (858,000 kilometers) from Prometheus and at a Sun-Prometheus-spacecraft, or phase, angle of 90 degrees. Image scale is 32 miles (51 kilometers) per pixel.

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

Saturn's North Polar Vortex and Rings

The Cassini spacecraft captures three magnificent sights at once: Saturn's north polar vortex and hexagon along with its expansive rings.

The hexagon, which is wider than two Earths, owes its appearance to the jet stream that forms its perimeter. The jet stream forms a six-lobed, stationary wave which wraps around the north polar regions at a latitude of roughly 77 degrees North.

This view looks toward the sunlit side of the rings from about 37 degrees above the ringplane. The image was taken with the Cassini spacecraft wide-angle camera on April 2, 2014 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 752 nanometers.

The view was obtained at a distance of approximately 1.4 million miles (2.2 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 43 degrees. Image scale is 81 miles (131 kilometers) per pixel.

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

Saturn's Shadows and Mimas

It may seem odd to think of planets casting shadows out in the inky blackness of space, but it is a common phenomenon. Earth’s shadow obscures the Moon during a lunar eclipse, and Jupiter’s moons cast small shadows onto their parent planet.

One of the best places in our Solar System to spot intriguing and beautiful celestial shadows is at Saturn. On 1 July, the international Cassini mission celebrates 10 years of exploring Saturn, its rings and its moons, an endeavor that has produced invaluable science but also stunning images like this.

Drifting along in the foreground, small and serene, is Saturn’s icy moon Mimas. The blue backdrop may at first appear to be the gas giant’s famous and impressive set of rings, with pale and dark regions separated by long inky black slashes, but it is actually the northern hemisphere of Saturn itself. The dark lines slicing across the frame are shadows cast by the rings onto the planet.

Although we may not associate the color blue with Saturn, when Cassini arrived at the planet the northernmost regions displayed the delicate blue palette shown in this image. As this region of Saturn is generally quite free of cloud, scattering by molecules in the atmosphere causes sunlight to take a longer path through the atmosphere. The light is scattered predominantly at shorter – bluer – wavelengths. This is similar to why the sky on Earth appears blue to our eyes.

Seasonal changes over the years since this photo was taken have turned the blue into Saturn's more familiar golden hue. The reverse is occurring in the south, which is slowly becoming bluer.

This image is composed of infrared, optical and ultraviolet observations from Cassini’s narrow-angle camera on 18 January 2005. The colors closely match what the scene would look like in true color.

This image was first published on the NASA Cassini website, in 2005.

Image credit: NASA/JPL/Space Science Institute

Atlas Emerging From Shadow

The Cassini spacecraft captures a glimpse of the moon Atlas shortly after emerging from Saturn's shadow. Although the sunlight at Saturn's distance is feeble compared to that at the Earth, objects cut off from the Sun within Saturn's shadow cool off considerably.

Scientists study how the moons around Saturn cool and warm as they enter and leave Saturn's shadow to better understand the physical properties of Saturn's moons.

This view looks toward the sunlit side of the rings from about 44 degrees above the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on January 23, 2014.

The view was acquired at a distance of approximately 1.6 million miles (2.6 million kilometers) from Atlas and at a Sun-Atlas-spacecraft, or phase, angle of 93 degrees. Image scale is 10 miles (16 kilometers) per pixel.

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

Saturn Ring Spokes

The spokes in Saturn's rings continue to be active and Cassini scientists continue to study them in order to unravel their mysteries. The spokes, visible near the center of the image, appear bright against the dense core of the B ring, which is the darkest section of the rings shown here in silhouette. Conditions favorable to the production of spokes are expected to wane as Saturn approaches its northern summer solstice. Scientists are eager to monitor the transition, the timing of which could yield valuable insight into the mechanisms that form these intriguing and ethereal features.

This view looks toward the unilluminated side of the rings from about 47 degrees below the ringplane. The image was taken in visible light with the Cassini spacecraft wide-angle camera on October 19, 2013.

The view was acquired 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 122 degrees. Image scale is 72 miles (115 kilometers) per pixel.

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

Saturn's C and B Rings in Ultraviolet Light

This colorful cosmic rainbow portrays a section of Saturn’s beautiful rings, four centuries after they were discovered by Galileo Galilei.

Saturn’s rings were first observed in 1610. Despite using his newly created telescope, Galileo was confounded by what he saw: he referred to the peculiar shapes surrounding the planet as “Saturn’s children”. Only later did Christiaan Huygens propose that the mysterious shapes were actually rings orbiting the planet. These were named in the order in which they were discovered, using the first seven letters of the alphabet: the D-ring is closest to the planet, followed by C, B, A, F, G and E.

The data for this image, which shows the portion of the C-ring closest to Saturn on the left, with the B-ring beginning just right of center, were acquired by Cassini’s Ultraviolet Imaging Spectrograph, or UVIS, as the spacecraft entered into orbit around Saturn on 30 June 2004.

UVIS, as its name suggests, carries out observations in ultraviolet wavelengths. During the Saturn orbit insertion maneuver, when Cassini flew closest to the rings, UVIS could resolve features up to 97 km across. The region shown in this image spans about 10,000 km.

The variation in the color of the rings arises from the differences in their composition. Turquoise-hued rings contain particles of nearly pure water ice, whereas reddish rings contain ice particles with more contaminants.

Saturn’s prominent and complex ensemble of rings is the best studied in the Solar System, but it is still not known how the rings formed. One suggestion is that they formed at the same time as the planet and that they are as old as the Solar System. Another idea is that they formed when icy material was pulled from another body into Saturn’s gravitational field, in which case the rings could be younger than the planet.

One thing is sure: as Cassini searches for answers it is providing amazing images of these rainbow rings.

The Cassini–Huygens mission is a cooperative project of NASA, ESA and Italy’s ASI space agency.

This image was first published at the NASA Cassini website, in 2004.

Image credit: NASA/JPL/University of Colorado

Uranus from Saturn

This view from NASA's Cassini spacecraft features a blue planet, but unlike the view from July 19, 2013 (PIA17172) that featured our home planet, this blue orb is Uranus, imaged by Cassini for the first time.

Uranus is a pale blue in this natural color image because its visible atmosphere contains methane gas and few aerosols or clouds. Methane on Uranus -- and its sapphire-colored sibling, Neptune -- absorbs red wavelengths of incoming sunlight, but allows blue wavelengths to escape back into space, resulting in the predominantly bluish color seen here. Cassini imaging scientists combined red, green and blue spectral filter images to create a final image that represents what human eyes might see from the vantage point of the spacecraft.

Uranus has been brightened by a factor of 4.5 to make it more easily visible. The outer portion of Saturn's A ring, seen at bottom right, has been brightened by a factor of two. The bright ring cutting across the image center is Saturn's narrow F ring.

Uranus was approximately 28.6 astronomical units from Cassini and Saturn when this view was obtained. An astronomical unit is the average distance from Earth to the sun, equal to 93,000,000 miles (150,000,000 kilometers).

This view was acquired by the Cassini narrow-angle camera at a distance of approximately 614,300 miles (988,600 kilometers) from Saturn on April 11, 2014. Image scale at Uranus is approximately 16,000 miles (25,700 kilometers) per pixel. Image scale at Saturn's rings is approximately 4 miles (6 kilometers) per pixel. In the image, the disk of Uranus is just barely resolved. The solar phase angle at Uranus, seen from Cassini, is 11.9 degrees.

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

Note: For more information, see Cassini Spies the Ice-Giant Planet Uranus.

Pan in the Encke Gap

Saturn's moon Pan, named for the Greek god of shepherds, rules over quite a different domain: the Encke gap in Saturn's rings.

Pan (17 miles, or 28 kilometers across) keeps the Encke gap open through its gravitational influence on the ring particles nearby.

This view looks toward the sunlit side of the rings from about 48 degrees above the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on December 25, 2013.

The view was obtained at a distance of approximately 1.4 million miles (2.3 million kilometers) from Pan and at a Sun-Pan-spacecraft, or phase, angle of 87 degrees. Image scale is 9 miles (14 kilometers) per pixel.

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

Possible New Moon Forming Around Saturn

The disturbance visible at the outer edge of Saturn's A ring in this image from NASA's Cassini spacecraft could be caused by an object replaying the birth process of icy moons.

The image is adapted from one in a paper in the journal Icarus, reporting the likely presence of an icy body causing gravitational effects on nearby ring particles, producing the bright feature visible at the ring's edge. The object, informally called "Peggy," is estimated to be no more than about half a mile, or one kilometer, in diameter. It may be in the process of migrating out of the ring, a process that one recent theory proposes as a step in the births of Saturn's several icy moons.

This image is a portion of an observation recorded by the narrow-angle camera of Cassini's imaging science subsystem on April 15, 2013. The bright feature at the edge of the A ring is about 750 miles (about 1,200 kilometers) long.

This view looks toward the illuminated side of the rings from about 53 degrees above the plane of the rings. It was obtained from a distance of approximately 775,000 miles (1.2 kilometers) from Saturn, with a sun-Saturn-spacecraft, or phase, angle of 31 degrees. The scale is about 4 miles (about 7 kilometers) per pixel.

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

Note: For more information, see NASA Cassini Images May Reveal Birth of a Saturn Moon and Possible New Moon Forming Around Saturn.

Prometheus and the F-Ring

Saturn's moon Prometheus orbits near some of its handiwork in the F ring.

Prometheus (53 miles, or 86 kilometers across) and its partner Pandora gravitationally sculpt and maintain the narrow F ring.

This view looks toward the unilluminated side of the rings from about 53 degrees below the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on August 24, 2013.

The view was acquired at a distance of approximately 1.1 million miles (1.8 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 104 degrees. Image scale is 7 miles (11 kilometers) per pixel.

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

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

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

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

Just as Saturn's famous hexagonal shaped jet stream encircles the planet's north pole, the rings encircle the planet, as seen from Cassini's position high above. Around and around everything goes!

This view looks toward the sunlit side of the rings from about 43 degrees above the ringplane. The image was taken with the Cassini spacecraft wide-angle camera on November 23, 2013 using a spectral filter that preferentially admits wavelengths of near-infrared light centered at 752 nanometers.

The view was obtained at a distance of approximately 1.6 million miles (2.5 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 97 degrees. Image scale is 93 miles (150 kilometers) per pixel.

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

Prometheus

Similar to many of the small, inner moons of Saturn, Prometheus points its long axis at Saturn as if giving us directions to the planet.

Prometheus (53 miles or 86 kilometers across), like most small moons, is not spherical. Astronomers think that the shapes of these moons hold clues to their origins and evolutions.

This view looks toward the sunlit side of the rings from about 37 degrees above the ringplane. 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 621,000 miles (1 million kilometers) from Prometheus and at a Sun-Prometheus-spacecraft, or phase, angle of 34 degrees. Image scale is 4 miles (6 kilometers) per pixel.

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