The Cassini Image Hall of Fame

 

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If you’re reading this, you’re probably very well aware of the Cassini mission. Launched in 1997, the Cassini spacecraft arrived at Saturn in June of 2004 and has been faithfully returning image after beautiful image of Saturn, its rings and its very extended family of moons ever since – not to mention all the groundbreaking scientific discoveries it’s made about the Saturnian system… and our solar system as a whole. Cassini truly is a rock star in the world of robotic space exploration, and now it has its own Hall of Fame to show off some of its best work!

The Cassini mission site put up by JPL/Caltech regularly features news and images from the mission, even including the latest downlinked raw image data from the spacecraft. In this way anyone can keep up with what Cassini is seeing and when, far before the images are included in NASA’s Planetary Data System. The new Cassini Image Hall of Fame showcases the “best of the best” from the mission, and is a great way to revisit Cassini’s past discoveries. (With so much happening at Saturn, sometimes it’s easy to forget all the amazing things Cassini has brought to our attention!)

Revisit the best of the best images of Saturn

If you’re a fan of Saturn (and really, who isn’t?) be sure to check this out. With the current mission extended into 2017 there’s sure to be lots more additions to the Hall of Fame on the way, too!

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. 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, Colorado.

Click here to see the Hall of Fame images.

Also, be sure to visit the hard-working Cassini imaging team’s homepage at http://ciclops.org… they are the ones responsible for all these fantastic images in the first place!

 

Water, Water Everywhere… And A Few Drops For Saturn, Too!

Recent Cassini images of Saturn's moon Enceladus backlit by the sun show the fountain-like sources of the fine spray of material that towers over the south polar region. This image was taken looking more or less broadside at the "tiger stripe" fractures observed in earlier Enceladus images. It shows discrete plumes of a variety of apparent sizes above the limb (edge) of the moon. This image was acquired on Nov. 27, 2005. Image Credit: NASA/JPL/Space Science Institute

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In 2005, NASA’s Cassini spacecraft gave us an incredible view of Enceladus chuffing out fountains of water vapor and ice. This action creates an enormous halo of gas, dust and ice that surrounds this Saturnian satellite and enables the planet’s E ring. Now Enceladus is once again in the spotlight as the only moon in the Solar System known to significantly contribute to its parent planet’s chemistry.

Earlier this year, ESA announced that its Herschel Space Observatory had observed a huge torus of water vapor around Saturn which apparently originated from Enceladus. It spans approximately 600,000 kilometers across and runs about 60,000 kilometers deep, but more so than its size is what it appears to be doing… adding water to Saturn’s upper atmosphere. Because the vapor isn’t detectable at visible wavelengths, this observation came as revelation for the Herschel scope.

“Herschel is providing dramatic new information about everything from planets in our own solar system to galaxies billions of light-years away,” said Paul Goldsmith, the NASA Herschel project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, California.

While the Herschel infrared observation is new, the indication of a vapor torus around Saturn isn’t. NASA’s Voyager and Hubble missions had given astronomers clues in the past. In 1997, the European Space Agency’s Infrared Space Observatory cited water in Saturn’s atmosphere and two years later NASA’s Submillimeter Wave Astronomy Satellite confirmed it again. But this confirmation only added up to a puzzle. Water found in Saturn’s lower cloud levels couldn’t rise past the colder, upper deck… So where was the water coming from? The answer came in the form of Herschel’s observations and some very astute computer modeling.

“What’s amazing is that the model, which is one iteration in a long line of cloud models, was built without knowledge of the observation.” says Tim Cassidy, a recent post-doctoral researcher at JPL who is now at the University of Colorado’s Laboratory for Atmospheric and Space Physics, Boulder. “Those of us in this small modeling community were using data from Cassini, Voyager and the Hubble telescope, along with established physics. We weren’t expecting such detailed ‘images’ of the torus, and the match between model and data was a wonderful surprise.”

Through these simulations, researchers hypothesized that much of the water in the torus was simply lost to space and some is pulled back by gravity to add material to Saturn’s rings. However, it’s the 3-5% that made it back to Saturn’s atmosphere that’s the most interesting. Just how much water vapor is out there? Thanks to combining information from both Herschel and the Ultraviolet Imaging Spectrograph (UVIS) instrument aboard the Cassini spacecraft, we’ve learned that about 12,000 kilograms is being ejected from Enceladus every minute. Can you image how much that would add up to in the period of a year… or more?!

“With the Herschel measurements of the torus from 2009 and 2010 and our cloud model, we were able to calculate a source rate for water vapor coming from Enceladus,” said Cassidy. “It agrees very closely with the UVIS finding, which used a completely different method.”

“We can see the water leaving Enceladus and we can detect the end product — atomic oxygen — in the Saturn system,” said Cassini UVIS science team member Candy Hansen, of the Planetary Science Institute, Tucson, Ariz. “It’s very nice with Herschel to track where it goes in the meantime.”

A tiny percentage adds up to some mighty big numbers, and the water molecules from the torus impact Saturn’s atmosphere to a great degree by contributing hydrogen and oxygen.

“When water hangs out in the torus, it is subject to the processes that dissociate water molecules,” said Hansen, “first to hydrogen and hydroxide, and then the hydroxide dissociates into hydrogen and atomic oxygen.” This oxygen is dispersed through the Saturn system. “Cassini discovered atomic oxygen on its approach to Saturn, before it went into orbit insertion. At the time, no one knew where it was coming from. Now we do.”

Very few days go by that we don’t learn something new about the Solar System and its inner workings. Thanks to observations like those done by the Herschel Space Observatory and missions like Cassini-Huygens, we’re able to further understand the dynamics behind the beauty… and how a tiny player can carry a major role.

“The profound effect this little moon Enceladus has on Saturn and its environment is astonishing,” said Hansen.

Original Story Source: JPL News Release.

Astronomy Cast Ep. 230: Christiaan Huygens

Christiaan Huygens

And now we finish our trilogy of Saturnian astronomers and missions with a look at the Dutch astronomer and mathematician, Christiaan Huygens. It was Huygens who discovered Titan, and figured out what Saturn’s rings really are, so it makes sense that a probe landing on the surface of Titan was named after him.

Click here to download the episode.

Or subscribe to: astronomycast.com/podcast.xml with your podcatching software.

“Christiaan Huygens” on the Astronomy Cast website.

Astronomy Cast Ep. 229: The Cassini Mission

Cassini Mission. Image credit: NASA/JPL/SSI

Last week we talked about the Italian astronomer Giovanni Cassini. This week we’ll talk about the mission that shares his name: NASA’s Cassini Spacecraft. This amazing mission is orbiting Saturn right now, sending back thousands of high resolution images of the ringed planet and its moons.

Click here to download the episode.

Or subscribe to: astronomycast.com/podcast.xml with your podcatching software.

Cassini Mission on the Astronomy Cast website.

A Close Look at Saturn’s Sponge Moon

This raw, unprocessed image of Hyperion was taken on August 25, 2011 and received on Earth August 26, 2011. Image credit: NASA/JPL-Caltech/Space Science Institute

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It might be one of the weirdest-looking moons in the solar system: Saturn’s moon Hyperion looks like a giant sponge. Additionally, its eccentric orbit makes it subject to gravitational forces from Saturn, so it is just tumbling along, almost out of control. Just yesterday, August 25, 2011, the Cassini spacecraft made a relatively close flyby of Hyperion (24,000 km 15,000 miles away) and took some amazing images.

“Hyperion is a small moon … just 168 miles across (270 kilometers)… orbiting between Titan and Iapetus,” said Carolyn Porco in an email. Porco is the Cassini imaging team lead. “It has an irregular shape and surface appearance, and it rotates chaotically as it tumbles along in orbit, making it impossible to say just exactly what terrain we would image during this flyby.”

See some more of the shots below:


Side view taken by NASA's Cassini spacecraft of Saturn's moon Hyperion. Image credit: NASA/JPL-Caltech/Space Science Institute

Scientists say this flyby’s closeness has likely allowed Cassini’s cameras to map new territory. At the very least, it will help scientists improve color measurements of the moon. It will also help them determine how the moon’s brightness changes as lighting and viewing conditions change, which can provide insight into the texture of the surface. The color measurements provide additional information about different materials on the moon’s deeply pitted surface.

A darker view of Hyperion. Credit: NASA/JPL-Caltech/Space Science Institute
NASA's Cassini spacecraft obtained this unprocessed image of Saturn's moon Hyperion on Aug. 25, 2011. Image credit: NASA/JPL-Caltech/Space Science Institute

The next closest pass of Hyperion is coming up again soon: Sept. 16, 2011, when it passes the tumbling moon at a distance of about 36,000 miles (58,000 kilometers).

See more raw images at the CICLOPS website.

Titan’s Giant Cloud Explained

This image from the Cassini spacecraft, shows a huge arrow-shaped storm measuring 1,500km in length. Image Credit: NASA/JPL/SSI

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Titan is making news again, this time with Cassini images from 2010 showing a storm nearly as big as Texas.  Jonathan Mitchell from UCLA and his research team have published their findings which help answer the question:

What could cause such large storms to develop on a freezing cold world?

For starters, the huge arrow isn’t a cosmic detour sign reminding us to “Attempt No Landings” on Jupiter’s moon Europa.

In the study by Mitchell and his team,  a model of Titan’s global weather was created to understand how atmospheric waves affect weather patterns on Titan.  During their research, the team discovered a “stenciling” effect that creates distinct cloud shapes, such as the arrow-shaped cloud shown in the Cassini image above.

“These atmospheric waves are somewhat like the natural, resonant vibration of a wine glass,” Mitchell said. “Individual clouds might ‘ring the bell,’ so to speak, and once the ringing starts, the clouds have to respond to that vibration.”

Titan is the only other body in the solar system (aside from Earth) known to have an active “liquid cycle”.  Much like Titan’s warmer cousin Earth, the small moon has an atmosphere primarily composed of Nitrogen.  Interestingly enough Titan’s atmosphere is roughly the same mass as Earth’s and has about 1.5 times the surface pressure.  At the extremely low temperatures on Titan, hydrocarbons such as methane appear in liquid form, rather than the gaseous form found on Earth.

With an active liquid both on the surface and in the atmosphere of Titan, clouds form and create rain. In the case of Titan, the rain on the plain is mainly methane.  Water on Titan is rock-hard, due to temperatures hovering around -200 c.

Studies of Titan show evidence of liquid runoff, rivers and lakes, further emphasizing Titan’s parallels to Earth. Researchers believe better understanding of Titan may offer clues to understanding Earth’s early atmosphere.  In another parallel to earth, the weather patterns on Titan created by the atmospheric waves can create intense rainstorms, sometimes with more than 20 times Titan’s average seasonal rainfall. These intense storms may cause erosion patterns that help form the rivers seen on Titan’s surface.  Mitchell described Titan’s climate as “all-tropics”,  basically comparing the weather to what is usually found near Earth’s equator.  Could these storms be Titan’s equivalent of  monsoon season?

Mitchell stated “Titan is like Earth’s strange sibling — the only other rocky body in the solar system that currently experiences rain”.  Mitchell also added, “In future work, we plan to extend our analysis to other Titan observations and make predictions of what clouds might be observed during the upcoming season”.

The research was published Aug. 14 in the online edition of the journal Nature Geoscience .

If you’d like to learn more about the Cassini mission, visit: http://saturn.jpl.nasa.gov/index.cfm

Cassini Surveys the Dunes of Xanadu on Titan

Three of Titan's major surface features-dunes, craters and the enigmatic Xanadu-appear in this radar image from NASA's Cassini spacecraft. Image credit: NASA/JPL-Caltech

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The name “Xanadu” just sounds exotic and enticing, and given that this region on Titan is right next to Shangri-la, how can we not be intrigued by the latest radar image of this region taken by the Cassini spacecraft? While Titan itself is shrouded in mystery with its thick, hazy atmosphere, via radar, Cassini can peer through and has found three major surface features: dunes, craters and the enigmatic Xanadu, a bright continent-sized feature centered near the moon’s equator. At upper right is the crater Ksa, first seen by Cassini in 2006. The dark lines running among Xanadu and Ksa are linear dunes, similar to sand dunes on Earth in Egypt and Namibia. In addition to the dunes, look closely at Xanadu to see hills, rivers and valleys which scientists believe are carved in ice rather than solid ground, by liquid methane or ethane.

This image was taken by Cassini’s Titan Radar Mapper on June 21, 2011.

Source: JPL

Cassini Focuses In On Two Moons

Image of Tethys and Titan taken in green visible light on July 14th 2011. Image Credit: NASA/JPL-Caltech/Space Science Institute

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In this new image from the Cassini Imaging Team Saturn’s moon Titan looks a little out of focus compared to the sharp, cratered surface of Tethys, seen in the foreground. But that’s only because Titan’s hazy atmosphere makes the moon look blurry. Titan’s current atmosphere is thought to resemble Earth’s early atmosphere, so we could be looking at an analog of early Earth.

And so, the Cassini mission is sharpening our understanding of Saturn and all its moons, but it might help us understand our own planet, as well.

At just over 1,000 kilometers in diameter, Tethys is believed to be almost entirely comprised of water ice, based on density estimates. Titan, at just over 5,000 kilometers in diameter is notable for being the second largest moon in our solar system, as well as having an atmosphere 1 1/2 times thicker than Earth. Titan is also known to have an active “liquid cycle” made up of various hydrocarbons, making Titan the second body in the solar system to have stable liquid on its surface.

The camera view is aimed at the Saturn-facing side of Titan and at the area between the trailing hemisphere and anti-Saturn side of Tethys. Not shown in frame is Saturn, which would be far to the left, from the perspective shown in the image.

The image was acquired with Cassini’s narrow-angle camera, in green visible light, on July 14, 2011. At a distance of roughly 3 million kilometers, the image scale for Titan is 19 kilometers per pixel. With Tethys at a distance of about 2 million kilometers, the image scale is roughly 11 kilometers per pixel.

If you’d like to learn more about the extended Cassini “solstice” mission, you can read more at: http://saturn.jpl.nasa.gov/mission/introduction/

Source: Cassini Solstice Mission Images

Cassini Captures a Menagerie of Moons

This Cassini raw image shows a portion of Saturn's rings along with several moons. How many can you find? Credit: NASA/JPL/Space Science Institute

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This stunning new Cassini image was captured on July 29, 2011, and shows a portion of Saturn’s rings along with several moons dotting the view. How many moons can you find, and can you name them?

See below for a color version of this image, put together by our own Jason Major!

Saturns moons and rings, in color. Credit: NASA / JPL / SSI. Edited by Jason Major. Click for larger version.

Jason shares on his Flickr page the process of how he edited the image. As Jason says, it’s a moon flash mob!

See the Cassini Solstice Mission raw images page for a larger view.

Hat tip to Stu Atkinson

The Sights And Sounds of Saturn’s Super Storm

The huge storm churning through the atmosphere in Saturn's northern hemisphere overtakes itself as it encircles the planet in this true-color view from NASA’s Cassini spacecraft. Image credit: NASA/JPL-Caltech/SSI

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It’s five hundred times bigger than any anything like it observed by the Cassini Mission in the last two years. It’s encompassing approximately 2 billion square miles (4 billion square kilometers) of Saturn’s surface. It’s releasing lightning bolts at a rate of ten per second and it’s happening ten times more frequently than other storms monitored since 2004. It’s so intense that’s it’s even visible in larger amateur telescopes. Just what is it? A Saturn Super Storm…

“Last December, a remarkable thing happened at Saturn. A massive, hissing, lightning-producing storm violently erupted in the northern mid-latitudes of Saturn’s atmosphere and grew to gargantuan proportions.” says Carolyn Porco. “By the end of January, it had wrapped itself entirely around the planet, developing an enormous degree of wavy, even sensuous, details, reminiscent of the clouds on Jupiter.”

Known as “Great White Spots”, these huge storms aren’t new to Saturn – they are common each Saturnian year. While they are common to the ringed planet’s northern summer, right now it’s northern spring. This makes the Saturn Super Storm an early – and unexpected – arrival.

“Prior to the planet’s August 2009 northern vernal equinox, when the sun was shining in the southern hemisphere, the location of all observed storm activity on Saturn was a band encircling the planet at 35 degrees south latitude that imaging scientists had dubbed `Storm Alley’. Well, to our great puzzlement, this new storm — now 500 times larger than any previously seen by Cassini at Saturn and 8 times the surface area of Earth — has erupted at 35 degrees /north/ latitude.” says Ms. Porco. “The shadow cast by Saturn’s rings has a strong seasonal effect, and it is possible that the switch to powerful storms now being located in the northern hemisphere is related to the change of seasons and the changing position of Saturn’s ring shadow. But why the obvious hemispheric symmetry in storm eruption exists is not yet known.”

NASA’s Cassini spacecraft was listening to the sounds of the storm, too. Much like our terrestrial lightning causes a static effect on an AM radio, Saturn creates a phenomena known as Saturn electrostatic discharges. Check out this audio file of the action!

“The storm is also a prodigious source of radio noise, which comes from lightning deep in the planet’s atmosphere. As on Earth, the lightning is produced in the water clouds, where falling rain and hail generate electricity. The mystery is why Saturn stores energy for decades and releases it all at once. This behavior is unlike that at Jupiter and Earth, which have numerous storms occurring at any one time.” explains Dr. Porco.

NASA's Cassini spacecraft captures a composite near-true-color view of the huge storm churning through the atmosphere in Saturn's northern hemisphere. Image credit: NASA/JPL-Caltech/SSI

Violent, yes… But incredibly beautiful. This false color image reveals clouds at different altitudes as seen by the Cassini spacecraft from a distance of approximately 1.5 million miles (2.4 million kilometers). Blue represents high and semi-transparent. Yellow and white are optically thick at high altitudes. Green is intermediate, while red and brown are low altitude unobscured by high clouds. Last, but not least is dark blue – a thin haze with nothing but Saturn below it. Scientists theorize the lightning is formed at the base cloud layer where water ice is covered by crystallized ammonia.

“This storm is thrilling because it shows how shifting seasons and solar illumination can dramatically stir up the weather on Saturn,” said Georg Fischer, a radio and plasma wave science team member at the Austrian Academy of Sciences in Graz. “We have been observing storms on Saturn for almost seven years, so tracking a storm so different from the others has put us at the edge of our seats.”

Original Story Source: JPL / NASA News.