Tuesday, February 25, 2014

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

Tuesday, February 18, 2014

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

Wednesday, February 12, 2014

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.

Tuesday, February 11, 2014

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

Wednesday, February 5, 2014

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

Tuesday, February 4, 2014

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