Daphnis and the Rings

Rather than being an unchanging disk of peaceful particles, the material that makes up Saturn's rings is constantly pushed and pulled into spectacular shapes.

On the left of the image, the moon Daphnis (8 kilometers,or 5 miles across) affects material as it orbits in the A ring's Keeler Gap. The moon's orbit is inclined relative to the plane of Saturn's rings. Daphnis' gravitational pull perturbs the orbits of the particles forming the Keeler Gap's edge. This sculpts the edge into waves having both horizontal (radial) and out-of-plane components. Material on the inner edge of the gap orbits faster than the moon so that the waves there lead the moon in its orbit. Material on the outer edge moves slower than the moon, so waves there trail the moon. See PIA11656 to learn more about this process.

On the right, the material at the edge of the Encke Gap shows waves caused by Pan (28 kilometers, or 17 miles across). See PIA09881 for a similar view.

This view looks toward the southern, unilluminated side of the rings from about 6 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 531,000 kilometers (330,000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 33 degrees. Image scale is 3 kilometers (2 miles) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Rhea, Janus and the Rings

The Cassini spacecraft looks past Saturn's rings and small moon Janus to spy the planet's second largest moon, Rhea.

Janus is closest to Cassini here. The rings are between Janus (179 kilometers, or 111 miles across) and Rhea (1,528 kilometers, or 949 miles across). Lit terrain seen on Rhea is on the leading hemisphere of that moon. This view looks toward the northern, sunlit side of the rings from just above the ringplane.

The image was taken in visible green light with the Cassini spacecraft narrow-angle camera on May 11, 2010. The view was obtained at a distance of approximately 3 million kilometers (2 million miles) from Rhea and approximately 2.4 million kilometers (1.5 million miles) from Janus. Image scale is 18 kilometers (11 miles) per pixel on Rhea. Image scale is 14 kilometers (9 miles) per pixel on Janus.

Photo credit: NASA/JPL/Space Science Institute

Ithaca Chasma

Sunlight illuminates the deep cut of Ithaca Chasma on Saturn's moon Tethys.

Ithaca Chasma runs roughly north-south for more than 1,000 kilometers (620 miles) on Tethys. See PIA07734 for a closer view.

Lit terrain seen here is on the Saturn-facing side of Tethys (1,062 kilometers, or 660 miles across). North on Tethys is up and rotated 18 degrees to the right.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on June 2, 2010. The view was obtained at a distance of approximately 477,000 kilometers (296,000 miles) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 127 degrees. Image scale is 3 kilometers (2 miles) per pixel.

Photo credit: NASA/JPL/Space Science Institute

The Shadows of the Rings

The shadow of Saturn's rings grows wider on the planet as the planet moves away from its August 2009 equinox, when the rings cast a pencil-thin shadow.

See PIA11667 for a view of Saturn with only a narrow shadow cast by the rings.

Saturn is overexposed here in order to show the dim rings. Pandora (below the rings to the left) has been brightened by a factor of 1.3 relative to the planet and the rings to enhance its visibility. The image was taken using a compression scheme that decreases image file size for storage onboard the spacecraft, and thus the image appears slightly blocky, or "pixelated" following enhancement.

This view looks toward the southern, unilluminated side of the rings from about 7 degrees below the ringplane.

The image was taken in visible light with the Cassini spacecraft wide-angle camera on June 24, 2010. The view was acquired at a distance of approximately 2.1 million kilometers (1.3 million miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 84 degrees. Image scale is 124 kilometers (77 miles) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Janus and Rings

Saturn's moon Janus orbits in front of the rings, which are partially darkened by the shadow of the planet in this Cassini spacecraft view.

Saturn's shadow obscures about half the rings. This can been seen on the left of the image, where a dark ring feature seems to stop abruptly as it meets the darkness of the planet's shadow above the edge of the bright rings.

This view looks toward the northern, sunlit side of the rings from just above the ringplane, and toward the leading hemisphere of Janus (179 kilometers, or 111 miles across). North on Janus is up. Janus is closer to Cassini than the rings are.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on April 10, 2010. The view was acquired at a distance of approximately 1.4 million kilometers (870,000 miles) from Janus and at a Sun-Janus-spacecraft, or phase, angle of 65 degrees. Image scale is 8 kilometers (5 miles) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Ontario Lacus

This image of Ontario Lacus, the largest lake on the southern hemisphere of Saturn's moon Titan, was obtained by NASA's Cassini spacecraft on January 12, 2010.

North is up in this image. Objects appear bright in this radar image when they are tilted toward the spacecraft or have rough surfaces. The lake surface appears dark because it is smooth.

The northern shoreline features flooded river valleys and hills as high as 1 kilometer (3,000 feet) in altitude.

A smooth, wave-sculpted shoreline, like that seen on the southeastern side of Lake Michigan, can be seen at the northeastern part of the lake. Smooth lines parallel to the current shoreline could be formed by low waves over time, which were likely driven by winds sweeping in from the west or southwest.

The southeast shore features a round-headed bay intruding into the shore. The liquid-filled depressions appear to be relatively recent.

The middle part of the western shoreline shows the first well-developed delta observed on Titan. The shape of the delta shows that liquid flowing down from a higher plain has switched channels on its way into the lake, forming at least two lobes. Examples of this kind of channel switching and wave-modified deltas can be found on Earth at the southern end of Lake Albert between Uganda and the Democratic Republic of Congo in Africa and the remains of an ancient lake known as Megachad in the African country Chad.

Titan is the only other world in our solar system known to have standing bodies of liquid on its surface. Because surface temperatures at the poles average a chilly 90 Kelvin (about minus 300 degrees Fahrenheit), the liquid is a combination of methane, ethane, and propane, rather than water. Ontario Lacus has a surface area of about 15,000 square kilometers (6,000 square miles), slightly smaller than its terrestrial namesake, Lake Ontario.

For an earlier image of Ontario Lacus obtained by Cassini's imaging cameras, see PIA06240.

Photo credit: NASA/JPL-Caltech

Janus, Prometheus and the Rings

A pair of Saturn's small, icy satellites accompany the planet's rings in this Cassini spacecraft snapshot.

Janus (179 kilometers, or 111 miles across) is farthest from Cassini here and occupies the top of the image. Prometheus (86 kilometers, or 53 miles across) orbits between the main rings and the thin F ring. The rings are between Janus and Prometheus. This view looks toward the northern, sunlit side of the rings from just above the ringplane.

The image was taken in visible green light with the Cassini spacecraft narrow-angle camera on April 9, 2010. The view was acquired at a distance of approximately 1 million kilometers (621,000 miles) from Prometheus and at a Sun-Prometheus-spacecraft, or phase, angle of 65 degrees. The view was acquired at a distance of approximately 1.1 million kilometers (684,000 miles) from Janus and at a Sun-Janus-spacecraft, or phase, angle of 65 degrees. Image scale is about 6 kilometers (4 miles) per pixel on Prometheus and about 7 kilometers (4 miles) per pixel on Janus.

Photo credit: NASA/JPL/Space Science Institute

Sliver of Iapetus

The Cassini spacecraft looks toward a crescent of Saturn's moon Iapetus and glimpses a bit of that moon's yin-yang appearance.

Scientists continue to investigate the nature of this moon's dark and light surface. See PIA11690 to learn more. Lit terrain seen here is in the transition area between the Saturn-facing side and trailing hemisphere of Iapetus (1,471 kilometers, or 914 miles across). North on Iapetus is roughly up and rotated 13 degrees to the left. The south pole is to left of the terminator at the bottom of the image.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on May 4, 2010. The view was obtained at a distance of approximately 1.4 million kilometers (870,000 miles) from Iapetus and at a Sun-Iapetus-spacecraft, or phase, angle of 130 degrees. Image scale is 9 kilometers (6 miles) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Mimas and Dione

The smaller moon Mimas upstages the larger moon Dione as the dramatic Herschel Crater is spotlighted on Mimas in this Cassini spacecraft view.

Herschel Crater is about 130 kilometers, or 81 miles, wide and covers a significant part of Mimas (396 kilometers, or 246 miles across) at the top of this picture. Smaller craters are visible on Dione (1,123 kilometers, or 698 miles across) in the lower portion of this image.

Because of the particular viewing geometry here, sunlight illuminates the leading hemisphere of Mimas on the left, and light reflected off Saturn dimly lights the Saturn-facing side of Mimas on the right. Lit terrain seen on the left of Dione is on the anti-Saturn side of that moon.

The image was taken in visible red light with the Cassini spacecraft narrow-angle camera on March 23, 2010. The view was obtained at a distance of approximately 1.6 million kilometers (994,000 miles) from Mimas and at a Sun-Mimas-spacecraft, or phase, angle of 87 degrees. The view was obtained at a distance of approximately 1.2 million kilometers (746,000 miles) from Dione and at a Sun-Dione-spacecraft, or phase, angle of 87 degrees. Image scale is 10 kilometers (6 miles) per pixel on Mimas and 7 kilometers (4 miles) per pixel on Dione.

Photo credit: NASA/JPL/Space Science Institute

Titan and Dione

Crisp details on Dione contrast with the haziness of Titan in this Cassini spacecraft image of a pair of Saturn's moons.

Smaller Dione is at the bottom of the image, and that moon's wispy terrain is visible. See PIA12608 to learn more about Dione's surface features. Titan dominates the rest of the image, and that moon's north polar hood is visible here. See PIA08137 to learn more about Titan's atmospheric haze.

Lit terrain seen here is on the trailing hemisphere of Dione (1,123 kilometers, or 698 miles across) and in the area between the trailing hemisphere and anti-Saturn side of Titan (5,150 kilometers, or 3,200 miles across).

The image was taken in visible blue light with the Cassini spacecraft narrow-angle camera on April 20, 2010. The view was obtained at a distance of approximately 2.3 million kilometers (1.4 million miles) from Dione and at a Sun-Dione-spacecraft, or phase, angle of 101 degrees. The view was obtained at a distance of approximately 1.3 million kilometers (808,000 miles) from Titan and at a Sun-Titan-spacecraft, or phase, angle of 101 degrees. Image scale is 14 kilometers (9 miles) per pixel on Dione and 8 kilometers (5 miles) per pixel on Titan.

Photo credit: NASA/JPL/Space Science Institute

Saturn

Roughly a quarter of majestic Saturn is illuminated in this view captured while the Cassini spacecraft was orbiting near the planet's equatorial plane.

This view looks toward the northern, sunlit side of the rings from just above the ringplane.

The image was taken in visible red light with the Cassini spacecraft wide-angle camera on November 25, 2009. The view was obtained at a distance of approximately 2 million kilometers (1.2 million miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 92 degrees. Image scale is 116 kilometers (72 miles) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Tethys' Melanthius Crater

The Cassini spacecraft looks toward an area between the trailing hemisphere and anti-Saturn side of Tethys and spies the large crater Melanthius near the moon's south pole.

Melanthius, at the bottom of this image, is about 250 kilometers (155 miles) wide on Tethys. See PIA10412 for another view. North on Tethys (1,062 kilometers, or 660 miles across) is up and rotated 19 degrees to the right.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on April 29, 2010. The view was acquired at a distance of approximately 670,000 kilometers (416,000 miles) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 41 degrees. Image scale is 4 kilometers (2 miles) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Prometheus and the Rings

Saturn's small, potato-shaped moon Prometheus orbits between the main rings and the thin F ring in this Cassini spacecraft view.

Prometheus can be seen just above the center of the image as it orbits in the Roche Division. The gravitational influence of Prometheus (86 kilometers, or 53 miles across) periodically creates streamer-channels in the F ring. To learn more and to watch a movie of this process, see PIA08397.

This view looks toward the northern, sunlit side of the rings from just above the ringplane.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on April 15, 2010. The view was acquired at a distance of approximately 2.6 million kilometers (1.6 million miles) from Prometheus. Image scale is 15 kilometers (9 miles) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Dione

Wispy terrain stretches across the trailing hemisphere of Saturn's moon Dione on the right of this Cassini image taken during the spacecraft's flyby on April 7, 2010.

See PIA06163 for an older, closer view of Dione's wispy fractures. This view looks toward the Saturn-facing side of Dione (1,123 kilometers, or 698 miles across). North on Dione is up and rotated 1 degree to the right.

The image was taken in visible light with the Cassini spacecraft wide-angle camera. The view was acquired at a distance of approximately 40,000 kilometers (25,000 miles) from Dione and at a Sun-Dione-spacecraft, or phase, angle of 11 degrees. Image scale is 2 kilometers (1 mile) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Earhart Propeller in the A Ring

A propeller-shaped structure created by an unseen moon is brightly illuminated on the sunlit side of Saturn's rings in this image obtained by NASA's Cassini spacecraft.

The moon, which is too small to be seen, is at the center of the propeller structure visible in the upper left of the image, near the Encke Gap of the A ring. The A ring is the outermost of Saturn's main rings.

The moon is likely about a kilometer (half a mile) across. Disturbed ring material to the upper left and lower right of the moon reflects sunlight brightly and appears like a white airplane propeller. Several density waves are also visible in the ring. A spiral density wave is a spiral-shaped accumulation of particles that tightly winds many times around the planet. It is the result of gravitational tugs by individual moons whose orbits are in resonance with the particles' orbits at a specific distance from Saturn.

A propeller's appearance changes with viewing geometry, and this image shows the way a propeller looks when viewed from the sunlit side of the rings. Contrasts can reverse when the structure is observed on the dark side of the rings: for example, the bright structure of this propeller corresponds to the dark portion at the center of the propeller seen in PIA12791 which was imaged from the unilluminated side of the rings.

This image is part of a growing catalog of "propeller" moons that, despite being too small to be seen, enhance their visibility by creating larger disturbances in the surrounding fabric of Saturn's rings. Cassini scientists now have tracked several of these individual propeller moons embedded in Saturn's disk over several years.

These images are important because they represent the first time scientists have been able to track the orbits of objects in space that are embedded in a disk of material. Continued monitoring of these objects may lead to direct observations of the interaction between a disk of material and embedded moons. Such interactions help scientists understand fundamental principles of how solar systems formed from disks of matter. Indeed, Cassini scientists have seen changes in the orbits of these moons, although they don't yet know exactly what causes these changes.

Imaging scientists nicknamed the propeller shown here "Earhart" after the early American aviatrix Amelia Earhart. The propeller structure is 5 kilometers (3 miles) in the radial dimension (the dimension moving outward from Saturn which is far out of frame to the lower right of this image). It is 60 kilometers (35 miles) in the azimuthal (longitudinal) dimension.

This same propeller can be seen casting a shadow around the time of the planet's equinox in PIA11672. See PIA07791 and PIA07792 to learn more about propeller shapes and to see smaller propellers.

Scale in the original image was 2 kilometers (1 mile) per pixel. The image has been rotated and contrast-enhanced to aid visibility.

This view looks toward the southern, sunlit side of the rings from about 81 degrees below the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on April 11, 2008. The view was obtained at a distance of approximately 364,000 kilometers (226,000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 82 degrees.

Photo credit: NASA/JPL/Space Science Institute

Note: For other images in this series, see PIA12789: Tracking a Propeller, PIA12791: Propeller from Unlit Side (mentioned above), and PIA12792: Propeller Churns the A Ring, which features a short movie of the Propeller "Bleriot," named after the French aviator Louis Blériot.

Enceladus

The Cassini spacecraft examines old and new terrain on Saturn's fascinating Enceladus, a moon where jets of water ice particles and vapor spew from the south pole.

Newly created terrain is at the bottom, in the center and on the left of this view. Older, cratered terrain is on the right. See PIA11685 for another view of this area and more information about its geology. This image was captured during Cassini's November 21, 2009, flyby of the moon. This view looks toward the leading hemisphere of Enceladus (504 kilometers, or 313 miles across). North on Enceladus is up and rotated 3 degrees to the right.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera. The view was obtained at a distance of approximately 133,000 kilometers (83,000 miles) from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 46 degrees. Image scale is 796 meters (2,612 feet) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Southern Cloud Swirls

Huge clouds swirl through the southern latitudes of Saturn where the rings cast dramatic shadows.

This view looks toward the northern, sunlit side of the rings from just above the ringplane.

The image was taken with the Cassini spacecraft wide-angle camera on April 30, 2010 using a spectral filter sensitive to wavelengths of near-infrared light centered at 728 nanometers. The view was obtained at a distance of approximately 1.4 million kilometers (870,000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 67 degrees. Image scale is 79 kilometers (49 miles) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Titan's Belet Region

The Cassini spacecraft looks toward Saturn's largest moon and maps the dark Belet region on Titan.

Lit terrain seen here is in the area between the trailing hemisphere and Saturn-facing side of Titan (5,150 kilometers, or 3,200 miles across). North on Titan is up.

The image was taken with the Cassini spacecraft narrow-angle camera on April 24, 2010 using a spectral filter sensitive to wavelengths of ultraviolet light centered at 938 nanometers. The view was acquired at a distance of approximately 1.9 million kilometers (1.2 million miles) from Titan and at a Sun-Titan-spacecraft, or phase, angle of 82 degrees. Image scale is 11 kilometers (7 miles) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Note: For some other recent photos of the Belet region, see The Belet Region of Titan and Close-up of Titan's Belet Region.

Herschel Crater on Mimas

Herschel Crater features prominently on the moon Mimas in this Cassini spacecraft image, which gives the impression of an eye staring out into space.

Herschel Crater is about 130 kilometers, or 81 miles, wide and covers a significant part of the moon. This view looks toward the leading hemisphere of Mimas (396 kilometers, or 246 miles across). North on Mimas is up and rotated 1 degree to the right.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on March 3, 2010. The view was acquired at a distance of approximately 476,000 kilometers (296,000 miles) from Mimas and at a Sun-Mimas-spacecraft, or phase, angle of 56 degrees. Image scale is 3 kilometers (2 miles) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Note: For an excellent close-up view of Herschel Crater, see this earlier post on one of my other blogs, Ministry of Space Exploration.

Janus and Pandora Amid the Rings

A pair of Saturn's small satellites, Janus and Pandora, accompany the planet's rings in this Cassini spacecraft image presenting the view in dramatic diagonal fashion.

The rings are between the two moons. Janus, just above the center of the image, is most distant here. This view looks toward the leading hemisphere of Pandora (81 kilometers, or 50 miles across) and the trailing hemisphere of Janus (179 kilometers, or 111 miles across). This view looks toward the northern, sunlit side of the rings from just above the ringplane.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on April 11, 2010. The view was acquired at a distance of approximately 1.9 million kilometers (1.2 million miles) from Janus and 1.8 million kilometers (1.1 million miles) from Pandora. Scale is about 11 kilometers (7 miles) per pixel on both moons.

Photo credit: NASA/JPL/Space Science Institute

Saturn and Mimas

A kingly crescent Saturn rests on the right of this Cassini spacecraft portrait while the moon Mimas appears above the rings on the left.

Mimas looks like just a speck of light here but is actually 396 kilometers, or 246 miles, across. This view looks toward the northern, sunlit side of the rings from just above the ringplane. Mimas was brightened by a factor of 1.4 relative to Saturn and the rings.

The image was taken with the Cassini spacecraft wide-angle camera on November 28, 2009 using a spectral filter sensitive to wavelengths of near-infrared light centered at 752 nanometers. The view was obtained at a distance of approximately 2.5 million kilometers (1.6 million miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 103 degrees. Image scale is 144 kilometers (89 miles) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Dione and Tethys

Saturn's moon Dione, in the foreground of this Cassini spacecraft image, appears darker than the moon Tethys.

Tethys appears brighter because it has a higher albedo than Dione, meaning Tethys reflects more sunlight. This higher albedo is due to Tethys being closer to the moon Enceladus and the E ring. Bright debris spews from Enceladus, feeding the E ring. This debris then coats Enceladus and Tethys with bright material. See PIA08921 and PIA11688 to see images of Enceladus's plume and the E ring.

Because of the viewing geometry, lit terrain seen here is on the anti-Saturn side of Dione (1,123 kilometers, or 698 miles across) and the leading hemisphere of Tethys (1,062 kilometers, or 660 miles across).

The image was taken in visible green light with the Cassini spacecraft narrow-angle camera on March 23, 2010. The view was obtained at a distance of approximately 1.2 million kilometers (746,000 miles) from Dione and at a Sun-Dione-spacecraft, or phase, angle of 88 degrees. The view was obtained at a distance of approximately 1.8 million kilometers (1.1 million miles) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 88 degrees. Image scale is 7 kilometers (4 miles) per pixel on Dione and 11 kilometers (7 miles) per pixel on Tethys.

Photo credit: NASA/JPL/Space Science Institute