That’s No Space Station. It’s a Moon!

TethysSaturn’s moon Tethys’s trailing side shows two terrains that tell a story of a rough past. To the north (up in this picture) is older, rougher terrain, while to the south is new material dubbed “smooth plains” by scientists. The smooth plains are roughly antipodal to the large impact crater Odysseus. Odysseus, which is on the far side of Tethys, is out of view. The leading theory is that the impact that created Odysseus also created the smooth plains, although exactly how this happened is not yet clear.

Image Credit: NASA

Pan and Zoom

Pan in the gap
Pan_zoomSaturn’s moon Pan, named for the Greek god of shepherds, rules over quite a different domain—the Encke gap in Saturn’s rings. See the inset at left for a zoomed in view. Pan (28 km 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 Christmas Day, 2013, from a distance of approximately 2.3 million km from Pan. The image scale is about 14 km) per pixel.

Image Credit: NASA

B and C in UV

RingsInUVOn 1 July, 2004, the Cassini spacecraft arrived at Saturn, marking the end of the spacecraft’s nearly seven-year journey through the solar system and the beginning of its tour of Saturn and the planet’s rings and moons.

This picture was taken in ultraviolet on 30 June, 2004 during Cassini’s orbital insertion maneuver. It shows, from left to right, the outer portion of the C ring and inner portion of the B ring which begins a little more than halfway across the image. The “dirty” particles are indicated by red, and “cleaner: ice particles shown in turquoise.

Saturn’s ring system is labeled from the inside out with the D, C, B and A rings followed by the F, G and E rings.

Image Credit: NASA

Rings and Shadows

ring shadowsjpgSaturn’s rings cast shadows on the planet, but the shadows appear to be inside out! The edge of Saturn’s outermost A ring can be seen at the top left corner of this picture taken by the Cassini spacecraft.  Moving down the image, one can see the faint Cassini Division, the opaque B ring, and the innermost C ring. The C ring contains several ringlets which appear dark against Saturn..  The bottom half of the picture shows the shadows of the rings in reverse order on the surface of the planet: the C ring, the B ring, the Cassini Division, and the inner half of the A ring.

Image Credit: NASA

New Moon?

new_moonThe Cassini spacecraft has documented the formation of a small icy object within the rings of Saturn that might be a new moon. It may also provide clues about the formation of some of the planet’s known moons.

Images taken with Cassini‘s narrow angle camera show disturbances at the very edge of Saturn’s A ring, the outermost of the planet’s large, bright rings. One of the disturbances is an arc about 1,200 km long and 10 km wide that is roughly 20 percent brighter than the surrounding ring.

The object is not expected to grow any larger, and may even be falling apart, but the process of its formation and outward movement in the ring aids in our understanding of how Saturn’s icy moons, including the cloud-wrapped Titan and ocean-holding Enceladus, may have formed in more massive rings long ago. It also provides insight into how Earth and other planets in our solar system may have formed and migrated away from the Sun.

Image Credit: NASA

Encountering Hyperion

This movie is a record of the Cassini spacecraft’s first close brush with Hyperion, a chaotically tumbling moon of Saturn. The jagged outlines are indicators of large impacts chipping away at Hyperion’s shape as a sculptor does to marble. The moon is too small to have pulled itself round by its own gravity. Its unusual dimensions are 328 by 260 by 214 km.

Video Credit: NASA

You Can’t See It From Here

Crescent SaturnThis is a view of Saturn partially lit in crescent phase, a view that can only be seen when the object is between the observer and the Sun. From the Earth, we can only see Mercury and Venus in varying crescent phases and Mars and the other outer planets fully lit. Because the Moon can be either between the Earth and the Sun or farther away, we see it go through all the phases from New to Full to New again.

This picture of Saturn was made by the Cassini spacecraft.

Image Credit: NASA

Saturn’s Rings in Infrared

Rings in IRHo, hum. Another picture of Saturn’s rings.

This one was made by the Cassini spacecraft using an infrared filter. The bright spot on the rings is the “opposition surge” where the Sun-Ring-Spacecraft angle passes through zero degrees. The size and magnitude of this bright spot to analyze the surface properties of the ring particles.

Image Credit: NASA

Titan and Rhea

Titan and RheaSaturn’s two largest moons, Titan and Rhea, seem to be stacked together in this true-color picture taken by the Cassini spacecraft. This view looks toward the Saturn-facing side of Rhea. North on Rhea is up and rotated 35 degrees to the right.

Separate images taken with red, green and blue filters using Cassini‘s narrow-angle camera were combined to create this natural-color view. The spacecraft was approximately 1.8 million km away from Rhea and 2.5 million km from Titan.

Image Credit: NASA


Southern WinterWinter is approaching in the southern hemisphere of Saturn, and with this even colder season has come a blue hue that was present in the northern winter hemisphere several years ago when the Cassini spacecraft arrived to orbit the planet. The blue hue that marks winter on Saturn is likely caused reduction of ultraviolet sunlight and the haze it produces. That allows the atmosphere to be clearer, increasing Rayleigh scattering (scattering by molecules and smaller particles) and methane absorption. Both processes make the atmosphere appear blue. The small black dot seen to the right and up from image center, within the ring shadows of the A and F rings, is the shadow of the moon, Prometheus.

Image Credit: NASA

Moons in the Rings

shepherd_moonsSome of Saturn’s smaller moons are integral with the planet’s rings. These moons create art on a canvas of the rings with gravity as their tool. Here Prometheus is seen sculpting the F ring while Daphnis (smaller than one pixel in this image) raises waves on the edges of the Keeler gap. The image scale is 11 km per pixel.

Prometheus (86 km across) is just above image center; Daphnis (8 km across) is in the Keeler gap just to the right of center and can be located by the waves it creates on the edges of the gap. Prometheus has been brightened to enhance their visibility in this picture. This visible light image looks toward the unlit side of the rings from below the ringplane.

Image Credit: NASA

Saturn’s Hexagon

hexagonThis animation was assembled using images from the Cassini spacecraft and is the highest-resolution view of the unique six-sided jet stream at Saturn’s north pole known as “The Hexagon.” It shows a complete view from the north pole down to about 70 degrees north latitude. The images have been rotated to account for the spin of the planet so that the point of view is as if we were in space above Saturn and rotating on its axis with it.

There is a wide variety of cloud structures within The Hexagon, including a massive hurricane tightly centered on the north pole, with an eye about 50 times larger than the average hurricane eye on Earth. There are numerous small vortices which show up as reddish ovals. Some of these vortices spin clockwise while The Hexagon and central hurricane spin counterclockwise. Some are swept along with the jet stream of The Hexagon. The biggest of these vortices, seen near the lower right, spans about 3,500 kilometers, roughly twice the size of the largest hurricane on Earth.

This is a false color movie in which different wavelengths of light from ultraviolet to visible to infrared have been assigned colors to enhance the contrast between the types of atmospheric particles inside and outside The Hexagon. On the inside there are fewer large haze particles and a concentration of small haze particles. Outside The Hexagon, the reverse is true. The jet stream that makes up the structure seems to act like a barrier, which results in something like the “ozone hole” in the Antarctic on Earth.

The Hexagon is an amazingly stable structure. Storms on Earth die out because of friction with the solid surface of the planet. Saturn is a gas giant. As summer returns to the its northern hemisphere, we will be watching for changes in The Hexagon.

Image Credit: NASA

Titan’s Southern Vortex

Titan_SouthernVortexThose of us who follow the Cassini mission are used to seeing pictures containing multiple moons of Saturn. That’s what I thought this was when I first saw it, but that small crescent isn’t a moon. It’s the storm vortex around Titan’s south pole. Its sunlit edge stands out distinctly against the darkness of the moon’s unilluminated hazy atmosphere. Cassini spacecraft images of the vortex have led scientists to conclude that its clouds form at a very high altitude—where the Sun has not yet set—above the surrounding haze near the moon’s surface.

Image Credit: NASA

You Are in This Picture

Click the image to embiggen. No, really, do it, and click on the new image a second time. You can use your BACK button to return.saturn_full_annotated

On 19 July, 2013,  the Cassini spacecraft slipped into Saturn’s shadow and turned to image the planet, seven of its moons, its inner rings,and—in the background—Earth.

With the Sun eclipsed by Saturn, Cassini‘s cameras were able to take advantage of this unusual viewing geometry. A panoramic mosaic of the Saturn system was taken that allows details in the rings backlit by the sun to be seen. This event was the third time Earth was imaged from the outer solar system.

Cassini captured 323 images in just over four hours. This final mosaic uses 141 of them. Images taken using the red, green, and blue spectral filters of the wide-angle camera were combined to create this natural-color view. This image spans a bit more than 650,000 km.

Make sure that you embiggen it and scroll around.

Image Credit: NASA

The Seasons Change on Titan

Titan_IRThis false-color picture was assembled from infrared data collected by the Cassini spacecraft. It show the differences in the composition of surface materials around hydrocarbon lakes at Titan, Saturn’s largest moon. With the Sun now shining on Titan’s northern hemisphere, the weather will be changing, and Cassini will be watching.

Learn more here.

Image Credit: NASA

An Unusual View of Saturn

saturn_irThis high-contrast, false-color mosaic from the Cassini spacecraft shows an infrared view of a slice of the Saturn system as it was backlit by the sun on 19 July, 2013. The exaggerated contrast brings out subtleties not initially visible. For example, structures in Saturn’s wispy E ring, which we believe to be made of ice from the moon Enceladus, stand out this exaggerated view.

The data for the image by Cassini’s visual and infrared mapping spectrometer. It covers a swath about 8,000 km wide across Saturn and its rings and about 540,000 km across that includes the planet and its rings out to the E ring, Saturn’s second most distant ring.

Image Credit: NASA

Saturn From Above

saturn20131017This view Saturn and its rings is a composite of images obtained by the Cassini spacecraft on 10 Octpber, 2013. It was assembled by a fan of the Cassini mission, amateur image processor Gordan Ugarkovic. The image has not been corrected for shifts in geometry caused the spacecraft’s changing  perspective as it moved.Also, it still has some camera artifacts. The mosaic was created from 12 image sets with red, blue and green filters from Cassini’s imaging science subsystem. Full color sets were used for 11 of the footprints, and red and blue images for one footprint.

Image Credit: Image credit: NASA / JPL-Caltech / Space Science Institute / G. Ugarkovic

The Big Storm on Saturn

saturn_storm_IR_visA couple of years ago, a huge storm occurred in the northern hemisphere of Saturn. This set of images from the Cassini spacecraft orbiting the planet shows the turbulent power of that monster storm. The visible-light image was taken on 25 February, 2011, and shows the turbulent clouds churning across the upper layers of Saturn’s atmosphere. The inset infrared image, obtained a day earlier using Cassini‘s visual and infrared mapping spectrometer, shows water and ammonia ices from deep in Saturn’s atmosphere being churned up to the top layers. This was the first time water ice was detected in Saturn’s atmosphere. The storm was first detected by Cassini‘s radio and plasma wave subsystem in December, 2010, and eventually wrapped around the planet.

Image Credit: NASA