F-Ring Perturbations

The F ring shows off a rich variety of phenomena in this image from the Cassini spacecraft. Near the lower-right of the F ring are two "fans" of material radiating out of the main strand (or "core") of the ring. Kinks are apparent all along the core, and dark "channels" cut into the main strand can be seen in places, the result of a recent interaction with the shepherd moon Prometheus (which cannot be seen in this image).

Scientists believe that many of the F ring's diverse features are the result of interactions between ring material and either the shepherd moons or clumps of material within the ring.

This view looks toward the sunlit side of the rings from about six degrees above the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on December 25, 2012.

The view was acquired at a distance of approximately 680,000 miles (1.1 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 17 degrees. Image scale is 4 miles (6 kilometers) per pixel.

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

Saturn's Bow Shock

The international Cassini spacecraft exploring the magnetic environment of Saturn. The image is not to scale. Saturn’s magnetosphere is depicted in grey, while the complex bow shock region – the shock wave in the solar wind that surrounds the magnetosphere – is shown in blue. While crossing the bow shock on 3 February 2007, Cassini recorded a particularly strong shock (an Alfvén Mach number of approximately 100) under a 'quasi-parallel' magnetic field configuration, during which significant particle acceleration was detected for the first time. The findings provide insight into particle acceleration at the shocks surrounding the remnants of supernova explosions.

Illustration credit: ESA

Note: For more information, see Cassini Sheds Light on Cosmic Particle Accelerators (ESA) and Cassini Sheds Light on Cosmic Particle Accelerators (JPL). Also, PIA16825: Magnetic Fields and Bow Shocks (Illustration) and PIA16739: Cassini at Saturn's Bow Shock (Artist Concept).

Vid Flumina Named

From the USGS Astrogeology Science Center:

The IAU Working Group for Planetary System Nomenclature has approved the name Vid Flumina for a channel on Titan. For more information, see the IAU Gazetteer of Planetary Nomenclature.

Note: Vid Flumina are a series of channels named after a broad river in Norse mythology of the ice-cold poisonous Elivagar system.

Crescent Rhea

The Cassini spacecraft captures Saturn's moon Rhea at crescent phase, a view never visible from Earth. Near the terminator, a few of Rhea's many craters show up in sharp relief.

With a diameter of 949 miles (1,528 kilometers) Rhea is Saturn's second-largest moon.

This view looks toward the leading hemisphere of Rhea. North on Rhea is up and rotated 12 degrees to the right.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on November 6, 2012. The view was obtained at a distance of approximately 1.2 million miles (1.9 million kilometers) from Rhea and at a Sun-Rhea-spacecraft, or phase, angle of 129 degrees. Scale in the original image was 7 miles (11 kilometers) per pixel. The image was magnified by a factor of 1.5 to enhance the visibility of surface features.

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

North Polar Hexagon and Rings

Saturn's north polar hexagon basks in the Sun's light now that spring has come to the northern hemisphere. Many smaller storms dot the north polar region and Saturn's signature rings, which appear to disappear on account of Saturn's shadow, put in an appearance in the background.

The north polar hexagon was first observed by Voyager. To see more of the hexagon, see PIA10486 and PIA11682.

The image was taken with the Cassini spacecraft's wide-angle camera on November 27, 2012 using a spectral filter sensitive to wavelengths of near-infrared light centered at 750 nanometers.

The view was acquired at a distance of approximately 403,000 miles (649,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 21 degrees. Image scale is 22 miles (35 kilometers) per pixel.

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

Northern Storm in Full Force

This mosaic of images from NASA's Cassini spacecraft shows the trail of a great northern storm on Saturn raging in full force. The contrast in the images has been enhanced to make the turbulent parts of the storm (in white) stand out without losing the details of the surrounding regions.

The head of the storm is the set of bright clouds near the left of the image. A clockwise-spinning vortex spawned by the storm shortly after it erupted in early December 2010 can be seen in the middle. The head of the storm moved very swiftly westward, while the vortex drifted more slowly westward.

Cassini's imaging camera obtained the images that went into this mosaic on March 6, 2011. The image is centered at about 0 degrees longitude and 35 degrees latitude.

In this image, scientists assigned red, green and blue channels to those visible-light colors. However, this view is not what a human eye would see at Saturn -- in enhancing the contrast, the natural color balance was not preserved. To human eyes, storm would have appeared more like a bright feature against a yellow background with less color variation, as is seen in PIA16724. In this color scheme, the brightness generally corresponds to the altitude of the cloud features. Bright white indicates highest cloud tops in the troposphere, and dark places indicate holes in the cloud layer. The subtle colors that become apparent in this enhanced-contrast view are probably produced by variation in the composition of clouds. However, the coloring agents responsible for producing these subtle hues remain unidentified.

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

First Chapter of the Northern Storm

This mosaic of false-color images from NASA's Cassini spacecraft shows what a giant storm in Saturn's northern hemisphere looked like about a month after it began. The bright head of the storm is on the left. The storm also spawned a clockwise-spinning vortex, seen as the light blue circular feature framed with a curl of bright clouds a little to the right of the storm head.

Cassini's imaging camera obtained the images that went into this mosaic on January 11, 2011. The storm erupted in early December 2010 and the head of the storm began moving rapidly westward. The vortex, spun off from the head of the storm in early December shortly after the storm began, drifted much more slowly. In August 2011, the head ran into the vortex, like a version of the mythical serpent that bites its own tail. By late August, the convective phase of the storm was over.

The colors indicate the altitudes of the clouds -- red is the lowest, green is an intermediate level and blue is the highest. White indicates thick clouds at a high altitude. Scientists assigned red to a wavelength of radiation that penetrates the atmosphere deep down to the top of the tropospheric cloud deck (750 nanometers). The troposphere is the part of the atmosphere where weather occurs. They assigned green to the 728-nanometer wavelength. Blue is a wavelength band that penetrates only to the top of tropospheric haze (890 nanometer).

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

Six Views of the Northern Hemisphere Vortex

A vortex that was part of a giant storm on Saturn slowly dissipates over time in this set of false color images from NASA's Cassini spacecraft. This clockwise vortex spun off the bright head of the storm shortly after the thunder-and-lightning storm erupted in early December 2010.

The top left image shows the vortex's most turbulent activity captured by Cassini's imaging cameras on January 11, 2011. It was centered around 54 degrees west longitude and 35 degrees north latitude. At the time, it was the largest vortex ever observed in Saturn's troposphere, which is the layer of the atmosphere where weather occurs. It measured up to 7,500 miles (12,000 kilometers) across. This is comparable in size to the giant storm on Jupiter known as Oval BA, though Oval BA and Jupiter's more famous storm -- the Great Red Spot -- are not thunder-and-lightning storms. Jupiter's vortices are known for their stability and longevity. Precursors to Oval BA formed in the 1930s, and evolved into what finally became Oval BA in the late 1990s. The Great Red Spot has been in existence at least since 1879, and possibly since 1664. Jupiter and Saturn are similar in many respects. However, why Jupiter's vortices are long-lived and why Saturnian ones are so short remain a mystery.

The image in the top middle was taken on March 17, 2011, when the center of the vortex had drifted west to around 6 degrees west longitude. The image on the top right was taken on April 25, 2011, when the vortex had moved to about 315 degrees west longitude.

The bright head of the storm was moving more quickly westward than the vortex and collided with the vortex by mid-June. The image at bottom left was obtained on July 12, 2011, after the head and vortex collided. The vortex here is less turbulent and is centered around 247 degrees west longitude. The bottom middle image was taken on August 24, 2011, about four days before the storm's thunder and lightning ceased completely. The vortex is swirling at about 218 degrees west longitude. The bottom right image was taken on October 6, 2011, when the vortex had nearly faded away. What is left of the vortex is centered around 248 degrees west longitude.The colors in these images denote the altitudes of the clouds – with red being the lowest, green being an intermediate level and blue being the highest. White indicates thick clouds at a high altitude. Scientists assigned the red color channel to a wavelength of radiation that penetrates the atmosphere deep down to the top of the tropospheric cloud deck (750 nanometers). They assigned blue to a wavelength that penetrates only to the top of tropospheric haze (890 nanometers). Green represents an intermediate wavelength above the troposphere (728 nanometers).

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

Note: For other images in this series, see PIA16722: Which Way the Wind Blows, PIA16723: Swirling Vortex, and PIA16724: Great Disturbances. Also, NASA's Cassini Watches Storm Choke on Its Own Tail.