Saturn Swirls

Atmospheric swirls on Saturn. Credit: NASA/JPL-Caltech/Space Science Institute

Atmospheric swirls on Saturn. Credit: NASA/JPL-Caltech/Space Science Institute

Originally meant to publish yesterday: Cassini took this image of the Saturn swirling atmosphere. Planetary atmospheres (including our own) are a study in fluid dynamics and that is clearly evident here.

The image was taken on 23 August 2014 in red light from about 1.8 million km / 1.1 million miles with the narrow-angle camera.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

Sunburn on Jupiter?

Cassini gives us clues about the Great Red Spot's color.

Cassini gives us clues about the Great Red Spot’s color.

New research on the Great Red Spot of Jupiter based on Cassini’s flyby nearly 14 years ago (Dec 2000) suggests the red color is from the “sunburn” of particles and the variable color comes from cloud altitudes.

From NASA:

The ruddy color of Jupiter’s Great Red Spot is likely a product of simple chemicals being broken apart by sunlight in the planet’s upper atmosphere, according to a new analysis of data from NASA’s Cassini mission. The results contradict the other leading theory for the origin of the spot’s striking color — that the reddish chemicals come from beneath Jupiter’s clouds.

The results are being presented this week by Kevin Baines, a Cassini team scientist based at NASA’s Jet Propulsion Laboratory, Pasadena, California, at the American Astronomical Society’s Division for Planetary Science Meeting in Tucson, Arizona.

Baines and JPL colleagues Bob Carlson and Tom Momary arrived at their conclusions using a combination of data from Cassini’s December 2000 Jupiter flyby and laboratory experiments.

In the lab, the researchers blasted ammonia and acetylene gases — chemicals known to exist on Jupiter — with ultraviolet light, to simulate the sun’s effects on these materials at the extreme heights of clouds in the Great Red Spot. This produced a reddish material, which the team compared to the Great Red Spot as observed by Cassini’s Visible and Infrared Mapping Spectrometer (VIMS). They found that the light-scattering properties of their red concoction nicely matched a model of the Great Red Spot in which the red-colored material is confined to the uppermost reaches of the giant cyclone-like feature.

“Our models suggest most of the Great Red Spot is actually pretty bland in color, beneath the upper cloud layer of reddish material,” said Baines. “Under the reddish ‘sunburn’ the clouds are probably whitish or grayish.” A coloring agent confined to the top of the clouds would be inconsistent with the competing theory, which posits that the spot’s red color is due to upwelling chemicals formed deep beneath the visible cloud layers, he said. If red material were being transported from below, it should be present at other altitudes as well, which would make the red spot redder still.
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Dione – A Global View

dionemap

NASA has produced global mosaics of Saturn’s moon Dione from Cassini spacecraft images. The image here is a trailing hemisphere which is darker than the leading hemisphere possibly because to “alteration by magnetospheric particles and radiation striking those surfaces”. It is also thought the leading hemisphere “is coated with icy dust from Saturn’s E-ring, formed from tiny particles ejected from Enceladus’ south pole. These satellites are all being painted by material erupted by neighboring Enceladus”.

The image is best enjoyed by looking at the high resolution verions at NASA’s Photojournal site you can see down to 250 meters per pixel – amazing!

Image Credit: NASA/JPL-Caltech/Space Science Institute/Lunar and Planetary Institute

A Dark Saturn

Saturn and Titan. Image Credit: NASA/JPL-Caltech/Space Science Institute

Saturn and Titan. Image Credit: NASA/JPL-Caltech/Space Science Institute

A look at a dark Saturn and Titan in this Cassini image. This view is looking pretty much towards the Sun providing a look at the atmosphere of Titan and a very nice crescent on both.

These observations can tell us something of the compositions and physical states of the atmospheres. You will notice the crescent goes almost all the way around Titan, this is due to small haze particles in the upper atmosphere refracting the sunlight.

For a sense of scale the view is from 1.7 million km or 1.1 million miles from Saturn and yet we don’t see the entire planet.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

via NASA’s Photojournal PIA18291

The Polar Hexagon

A close look at Saturn's north polar vortex. Click for larger. Image Credit: NASA/JPL-Caltech/Space Science Institute

A close look at Saturn’s north polar vortex. Click for larger. Image Credit: NASA/JPL-Caltech/Space Science Institute

Another very nice look at the north polar hexagon of Saturn from the Cassini spacecraft. This view is from 973,000 km/605,000 miles from about 33 degrees above the ring plane on 24 July 2013.

What causes the hexagon is not fully understood, the thinking is a “meandering” polar jet stream. Apparently wind speed is less important than the gradient of the winds flowing around the area in the formation of the hexagon which seem a little counter intuitive.

Another nice part of the photo is the detail in the atmosphere. Storms on Saturn are thought to occur when relatively warm atmospheric gas in the depths of the planet rise and cool, causing gaseous ammonia to form crystals and white clouds. This is analogous to thunderstorms here on Earth.

For more on the hexagon from NASA click here.

DON’T FORGET ABOUT THE TOTAL LUNAR ECLIPSE TONIGHT – CLICK HERE FOR DETAILS!!

Changing Feature on Titan

Images showing changes in the Ligeia Mare on Titan. Click for larger. Image Credit: NASA/JPL-Caltech/ASI/Cornell

Images showing changes in the Ligeia Mare on Titan. Click for larger. Image Credit: NASA/JPL-Caltech/ASI/Cornell

Shifting patterns in the Titan landscape. Cool stuff indeed. This is the only place we’ve seen liquid seas/oceans beyond Earth, volcano’s yes, liquid oceans no. Ok so the seas/oceans on the Saturn moon Titan are mostly ethane and methane, still counts. Now enough history in images has been collected we can see changes in the seas/oceans structure, thanks to this great mission.

The press release offers possible explanations, could be as simple as well, gee I’m not sure, what would an “ice” berg be called if it was a hydrocarbon? A petrolberg or something I would guess.

As an aside, while I was spending my day painting the observatory (and finding a huge problem) I was thinking: what a good value these orbiting wonders are.

From the Cassini site:

These three images, created from Cassini Synthetic Aperture Radar (SAR) data, show the appearance and evolution of a mysterious feature in Ligeia Mare, one of the largest hydrocarbon seas on Saturn’s moon Titan. The views, taken during three different Cassini flybys of Titan, show that this feature was not visible in earlier radar images of the same region and its appearance changed between 2013 and 2014.

In the images, the dark areas represent the sea, which is thought to be composed of mostly methane and ethane. Most of the bright areas represent land surface above or just beneath the water line. The mysterious bright feature appears off the coast below center in the middle and right images.
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A Trio of Moons

A trio of Saturn moons from the Cassini spacecraft. Image Credit: NASA/JPL-Caltech/Space Science Institute

A trio of Saturn moons from the Cassini spacecraft. Image Credit: NASA/JPL-Caltech/Space Science Institute

A nice Cassini image of three of Saturn’s moons and the expanse of rings taken at a low angle.

The largest of the three is Tethys, moving to the left we have the weirdest of the three and my personal favorite moon, Hyperion.

The last of the three is the one I call the potato, Prometheus, you will find it in the foreground right into to the edge of the rings. Actually Prometheus is inside the F ring, it has a partner on the outside of the F ring not shown here called Pandora. These two moons are known as shepherd moons and they keep the F ring nice and tidy.

Then there are the rings, the low angle perspective shows exquisite detail.

Be sure to pay a visit to our Saturn page and scroll down to the “Saturn’s Satellite” section and click on the image to the right for a guide.

See the original image at JPL

A Crescent Mimas

The crescent of the battered Mimas. Credit: NASA/JPL-Caltech/Space Science Institute

The crescent of the battered Mimas. Credit: NASA/JPL-Caltech/Space Science Institute

The Saturn moon Mimas was the target of Cassini’s cameras. One of the striking features of the moon is a crater known as Herschel. Herschel can be seen in the shadows at about the five o’clock position.

More about Mimas and a great look at the crater Herschel can be found here.

About the image from the Cassini site:

A thin sliver of Mimas is illuminated, the long shadows showing off its many craters, indicators of the moon’s violent history.
The most famous evidence of a collision on Mimas (246 miles, or 396 kilometers across) is the crater Herschel that gives Mimas its Death Star-like appearance. See Examining Herschel Crater for more on Herschel.

This view looks toward the anti-Saturn hemisphere of Mimas. North on Mimas is up and rotated 40 degrees to the right. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on May 20, 2013.

The view was acquired at a distance of approximately 100,000 miles (200,000 kilometers) from Mimas and at a Sun-Mimas-spacecraft, or phase, angle of 130 degrees. Image scale is 4,000 feet (1 kilometer) per pixel.
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The North of Saturn

The north of Saturn from Cassini.  Image: NASA/JPL-Caltech/Space Science Institute

The north of Saturn from Cassini. Image: NASA/JPL-Caltech/Space Science Institute

A great image of Saturn from the Cassini spacecraft. Click the image above to see some of the detail in the atmosphere. Saturn’s atmospheric zones resemble the ones on Jupiter but thanks to lower surface gravity the clouds are more spread out, so are less defined. Saturn’s atmosphere is also colder than Jupiter as you might expect.

Like Jupiter, Saturn radiates more energy into space than it receives from the sun. What you might not expect is when size is taken into account, Saturn radiates more energy into space from its interior than Jupiter – by about 25 percent.

NASA calls this release The Ring King and for good reason:

Saturn reigns supreme, encircled by its retinue of rings. Although all four giant planets have ring systems, Saturn’s is by far the most massive and impressive. Scientists are trying to understand why by studying how the rings have formed and how they have evolved over time. Also seen in this image is Saturn’s famous north polar vortex and hexagon. This view looks toward the sunlit side of the rings from about 37 degrees above the ringplane. The image was taken with the Cassini spacecraft wide-angle camera on May 4, 2014 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 752 nanometers. The view was acquired at a distance of approximately 2 million miles (3 million kilometers) from Saturn. Image scale is 110 miles (180 kilometers) per pixel. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

The Eye of Saturn

A new look at the northern polar vortex on Saturn.  Credit: NASA/JPL-Caltech/Space Science Institute

A new look at the northern polar vortex on Saturn. Credit: NASA/JPL-Caltech/Space Science Institute

Not really an eye of course, but it kind of looks like one.  This is a close up view of the northern polar vortex on Saturn taken from the Cassini spacecraft.  I enlarged the image and enhanced it a little to bring out the details a little more.  You can see the original here.

That “eye” is 2,000 km / 1,240 miles across, you can see clouds as them move some 150 meters per sec / 330 miles per hour.

Cassini was 2.2 million km / 1.4 million miles from Saturn at the time the image was taken.