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

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

Land of Lakes

Titan is the only body in the Solar System other than the Earth with stable areas of liquid on its surface.

Video 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

Not a Solar Eclipse

titanbusy_cassini_960No, it’s not a solar eclipse. It’s a picture of the rings and a couple of the moons of Saturn. The large object near the center is Titan, Saturn’s largest moon and one of the most interesting objects in the entire Solar System. The central dark spot is the body of the moon. The bright halo is atmospheric haze above Titan. The gases of the atmosphere scatter sunlight. Saturn’s rings are shown nearly edge on. Enceladus, a small moon, is at about 4 or 5 o’clock at the edge of Titan.

This image was taken with the Cassini spacecraft’s camera pointing almost directly at the Sun, so the surfaces of Titan and Enceladus appear in silhouette, and the rings of Saturn look like a photographic negative.

Image Credit: NASA

You Are Here—In Color

earth-moon_from_saturnLast Friday, the Cassini spacecraft was able to take a picture of the Earth from the spacecraft’s orbit around Saturn. This morning, I posted a black-and-white portion of this larger view taken by Cassini‘s wide-angle camera. Here’s the entire image. Click it to embiggen. Go ahead. It’s worth it. You can use your back button to return.

The dark side of Saturn, its bright limb, the main rings, the F ring, and the G and E rings are visible. The limb of Saturn and the F ring are overexposed. The “breaks” in the brightness of Saturn’s limb are shadows of the rings The E and G rings have been brightened through post processing for better visibility.

Earth, which is 1.44 billion km away in this image, is that blue dot indicated by the arrow. In the full-size image the Moon can be seen as a fainter protrusion off its right side. The other bright dots are stars

This is only the third time that Earth has been photographed from the outer solar system.

Image Credit: NASA

You Are Here

earthmoon_cassini_960This is the Earth-Moon system as seen by the Cassini spacecraft orbiting Saturn in the outer Solar System. Earth is the larger of the two spots near the center; the Moon is to its lower left. This raw, unprocessed image shows several streaks that are not stars. They are cosmic rays that struck the digital camera while it was taking the image. The image was taken by Cassini on Friday.

Image Credit: NASA

Say “Cheese”

This afternoon from 21:27 to 21:42 UTC (5:27 to 5:42 pm ET), the planet Saturn will be between the Cassini spacecraft and the Sun. The spacecraft will use that opportunity to photograph the Earth at a range of around 1.4 billion kilometers.

There have been only two images of Earth from the outer solar system in all the time we’ve been venturing out into space. The first and most distant was taken 23 years ago by the Voyager 1 spacecraft from 6 billion kilometers away. Earth appears as a pale blue dot. The other was a Cassini image taken in 2006 from about 1.5 billion kilometers.

Smile and wave.

Titan’s Southern Sea

Titan_southern_seaOr what’s left of it. The red outline traces the ancient shoreline. The largest remaining lake in Titan’s southern hemisphere, Ontario Lacus appears as black within that basin. The black indicated that it is filled with liquid.

This picture is assembled from images was obtained by the Cassini spacecraft’s radar instrument during July, 2009, and January, 2010. Mission scientists estimate the ancient sea was possibly as large as 475 X 280 km across but probably only a few hundred meters deep. Ontario Lacus is about 80 X 235 km and probably on the order of 10 meters deep. Seas may have covered large parts of Titan’s southern hemisphere less than 50,000 years ago.

Titan, Saturn’s largest moon, is the only body in the Solar System other than the Earth that has large open bodies of liquid. The temperature on Titan runs around 94 K (about -290 °F), so that liquid is not water. It’s methane and ethane. While over one hundred lakes and three seas are seen around Titan’s north pole, the south pole only has a few small lakes. It’s been suggested that cycles similar to Milankovich cycles on Earth cause long-term transfers of liquid hydrocarbons between the poles and that it’s now the north poles turn to keep the bulk of the liquids. Less than 50,000 years ago, the cycle may have reversed, nearly emptying the southern seas.

Image Credit: NASA

Thunder and Lightning on Saturn

head_to_tailThis collection of images from the Cassini spacecraft orbiting Saturn shows the evolution of a massive thunder storm that circled all the way around the planet and fizzled out when it ran into its own tail. The storm was first detected on 5 December, 2010. It developed a head of bright clouds which began rapidly moving west and also spawned a much slower moving clockwise-spinning vortex.

The bright clouds at the head of the storm are indicated with red triangles. Yellow triangles mark the vortex.

The top image was taken not long after the start of the storm on 22 January, 2011. It shows the bright head of the storm just ahead of the vortex by about 40,000 km. The next image from 5 May shows that the head of the storm had traveled around the planet and started approaching the vortex from the east. The storm’s body had stretched over 220,000 km, and the head was within about 80,000 km of the vortex. That image also shows that the  vortex was losing steam compared to the head of the storm. The third image was taken on 14 June. The head of the storm had made its way roughly 290,000 km—almost entirely around the planet, and it was about to catch up with the vortex. The head of the storm was just 14,000 km east of the vortex. The bottom image, from 12 July, 2011, shows that the storm fizzled once the head and vortex met. Only the vortex remains; the bright cloud has disappeared. By late August, the storm stopped generating lightning for good.

These are false color images with the colors denoting the altitudes of the clouds. Red data is from a wavelength of radiation that penetrates the atmosphere deep down to the top of the tropospheric cloud deck (750 nm). Green represents an intermediate wavelength above the troposphere (728 nm). Blue is for a wavelength that penetrates only to the top of tropospheric haze (890 nm). White is for thick clouds at high altitudes.

Image Credit: NASA