New radar images from Encealdus' south pole show high amounts of surface texturing. NASA/JPL-Caltech/SSI.
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Cassini’s done it again! Soaring over Saturn’s moon Enceladus back on November 6, the spacecraft obtained the highest-resolution images yet of the moon’s south polar terrain, revealing surface details with visible, infrared and radar imaging that have never been seen before.
Of particular interest are new image swaths acquired by the spacecraft’s synthetic-aperture radar (SAR) instrument, which has never before been used on Enceladus. The radar, which is highly sensitive to surface textures, reveals some extremely bright regions that have surprised scientists.
Detail of the radar-imaged area (enlarged). NASA/JPL-Caltech/SSI.
“It’s puzzling why this is some of the brightest stuff Cassini has seen,” said Steve Wall, deputy team lead of Cassini’s radar team based at NASA’s Jet Propulsion Laboratory in Pasadena. “One possibility is that the area is studded with rounded ice rocks. But we can’t yet explain how that would happen.”
The SAR images did not focus on the moon’s now-famous “tiger stripe” fractures (called sulci) which are the sources of its icy jets. Instead, Cassini scanned areas a few hundred miles around the stripes. These regions have not been extensively imaged before and this new data shows surface patterns and elevations that had been previously unknown.
Some of the steep grooves in the imaged areas were shown to be as deep as 2,100 feet (650 m), and 1.2 miles (2 km) wide.
Cassini passed by the 318-mile (511-km) -wide moon at 04:49 UTC on November 6, 2011. Cassini’s radar instrument was built by JPL and the Italian Space Agency, working with team members from the U.S. and several European countries. Previously used to image the surface of Titan, which is hidden from view by a thick atmosphere, this is the first time the instrument was used on Enceladus.
In 1989, meteorologists discovered sprites. Not the spirits, elves, or pixies that pepper Shakespearean comedies but their equally elusive electrical namesakes. Lightning sprites are large scale electrical discharges inside the clouds above storms that make the upper atmosphere glow, sort of like a fluorescent lightbulb.
Meteorologists have already determined that sprites likely aren’t unique to Earth. In fact, this elusive form of lightning might be common throughout the solar system. Now, researchers at Tel Aviv University are asking whether the presence of sprites on other planets could indicate the presence of organic material in their atmospheres.
The layers of our atmosphere. Image credit: National Weather Service, JetStream Online School for Weather.
Though not an uncommon phenomena, sprites are incredibly hard to find and observe. They can only be captured with highly sensitive high speed cameras. Sprites occur in the Earth’s Mesosphere, layer between the stratosphere and the thermosphere – about 50 km (31 miles) to 90 km (56 miles) high. At this altitude, the gases that make up our atmosphere are much thinner and unable to hold heat from the Sun making the average temperature a chilly 5°F (-15°C) to as low as -184°F (-120°C).
But gases at this altitude are still thick enough to slow meteors – this is where they burn up and create what we see as meteor showers. Gases in the mesosphere are also thick enough to light up with sprites, providing a window into the composition of our atmosphere. Sprites, which glow reddish-orange, indicate the kinds of molecules present in this layer of the atmosphere.
Lightning isn’t a rare occurrence in our solar system, which leads researchers to suspect sprites might be found on Jupiter, Saturn, and Venus – all planets with the right environment for strong electrical storms. Just like on Earth, sprites found on these planets could open a window in their atmospheric composition, conductivity, and possibly point to the presence of exotic compounds.
Jupiter and Saturn present the most exciting environments. Both gas giants experience lightening storms with flashes more than 1,000 as powerful as those found on Earth. It’s on these planets that Ph.D. student Daria Dubrovin, with her supervisors Prof. Colin Price of Tel Aviv University’s Department of Geophysics and Planetary Sciences and Prof. Yoav Yair at the Open University of Israel, is focussing on.
Dubrovin has re-created these planetary atmospheres in a lab to study the presence of sprites in space. Or, as she describes her work, “We make sprites in a bottle.” She hopes this will provide a new understanding of electrical and chemical processes on other planets.
A sprite as it might appear in Saturn's atmosphere, created in a TAU lab. Image credit: American Friends, Tel Aviv University
What’s more, understanding lightning on other worlds could help researchers understand the possibility of life on other worlds. As Dubrovin points out, lightning is commonly accepted as the generator of organic molecules that turned early Earth’s ocean into the life-filled primordial soup. Increased study of lightning on other planets could give another clue into the presence of extraterrestrial life. Their research could easily be applied to exoplanets, not just bodies in our solar system.
A lightning storm on Saturn has Dubrovin pretty excited. It’s currently producing over 100 electrical flashes per second, a rare occurrence even within the planet’s volatile cloud layers. If researchers could successfully gather images of higher altitude sprites from the Cassini spacecraft (currently in orbit around Saturn), it would not only yield information on the storm below but also add to the general knowledge base of sprites and lightning on other planets.
Saturn's northern storm marches through the planet's atmosphere in the top right of this false-color mosaic from NASA's Cassini spacecraft. Credit: NASA/JPL-Caltech/Space Science Institute
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Nearly a year ago a small, bright white storm emerged on Saturn’s northern hemisphere. This storm has now wrapped around the planet, creating a colossal atmospheric disturbance that has become the largest storm seen on the planet since 1990. And the Cassini spacecraft has been there to see it all.
“It is the singular distinction of being in orbit, and able to turn a scrutinizing eye wherever it is needed, that has allowed us to be present to witness this extraordinary phenomenon,” said Carolyn Porco, the Cassini Imaging Team Leader. “The storm has spread to become a planet-encircling colossus, a wide kaleidoscopic band of commingled waves, vortices, and eddies, all in continuous swirling motion …. a mesmerizing display of snaking, sensuous, churning, turning, chaotic, roiling atmospheric turmoil.”
If Porco sounds like she’s waxing poetic, she has good reason. The images put out by the Cassini imaging team today are a “sublime visual extravaganza,” and both true and false color images are gorgeous to behold.
This is nearly true-color view by Cassini of the storm. Credit: Credit: NASA/JPL-Caltech/Space Science Institute
The huge storm extends around Saturn’s northern hemisphere and from north to south spread approximately 9,000 miles, or 15,000 kilometers. It has become the largest observed on Saturn in the past 21 years, and the largest by far ever observed on the planet from an interplanetary spacecraft. What timing for Cassini to be there!
“Seven years of chasing such opportunities across the solar system’s most magnificent planetary system have already made Cassini one of the most scientifically productive planetary missions ever flown,” said Porco on the CICLOPS website. “And with any luck, there’ll be a great deal more to come.”
These false-color mosaics from NASA's Cassini spacecraft chronicle the changing appearance of the huge storm that developed from a small spot in Saturn's northern hemisphere. Here Cassini captures the changes over the short time span of one Saturn day; the two images were taken 11 hours apart. Credit: NASA/JPL-Caltech/Space Science Institute
Cassini has taken hundreds of images of this storm as part of the imaging team’s “Saturn Storm Watch” campaign. Cassini has been able to take quick looks at the storm in between other scheduled observations, of either Saturn or its rings and moons.
Other instruments on Cassini have detected the storm’s electrical activity and revealed it to be a convective thunderstorm. Its active convecting phase ended in late June, but the turbulent clouds it created linger in the atmosphere today.
“The Saturn storm is more like a volcano than a terrestrial weather system,” said Andrew Ingersoll, a Cassini imaging team member at the California Institute of Technology in Pasadena, Calif. “The pressure builds up for many years before the storm erupts. The mystery is that’s there’s no rock to resist the pressure – to delay the eruption for so many years.”
This storm’s 200-day active period makes it the longest-lasting planet-encircling storm ever seen on Saturn. The previous record holder was an outburst sighted in 1903 which lingered for 150 days. The large disturbance imaged 21 years ago by NASA’s Hubble Space Telescope was comparable in size to the current storm. That 1990 storm lasted for only 55 days.
This series of images from NASA's Cassini spacecraft shows the development of the largest storm seen on the planet since 1990. Credit: NASA/JPL-Caltech/Space Science Institut
Enceladus and Epimetheus as seen by Cassini on October 1, 2011.
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Taken during the Cassini spacecraft’s October 1 flyby of Saturn’s ice-spewing moon, this image – released today – shows a crescent-lit Enceladus with southern geysers in action… and the much smaller Epimetheus peeking out from behind!
Epimetheus
The 70-mile (113-km) -wide Epimetheus is dwarfed by its larger sibling Enceladus, which is 313 miles (504 km) in diameter… about the width of the state of Arizona.
One of the most reflective objects in the solar system, Enceladus appears to be casting some reflected light onto Epimetheus as well. (Image processors at the Cassini Imaging Lab have brightened the moons by a factor of 1.8 relative to the rings in order to bring out detail.)
Some bright clumps of material can also be seen orbiting within Saturn’s rings at upper left, possibly stirred up by the movement of the shepherd moon Pan.
In this image an Orion MultiPurpose Crew Vehicle jettison motor or JM, which is produced by Aerojet is test-fired. Photo Credit: Aerojet
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When it comes to space flight pedigrees, few companies have one that can compare to Aerojet’s. The California-based company has a resume on space operations that is as lengthy as it is impressive. Universe Today sat down with Julie Van Kleeck – the firm’s vice-president of space and launch systems business unit.
Van Kleeck spoke extensively about the company’s rich history, its legacy of accomplishments – as well as what it has planned for space missions of the future.
Universe Today:Hi Julie, thanks for taking the time to chat with us today.
Van Kleeck: “My pleasure!”
Universe Today:How long has Aerojet been in business and what exactly is it that your company produces?
Van Kleeck: “We’ve been in the space business – since there was a space program – so since at least the 50s. We’ve dealt with both launch systems as well as space maneuvering systems, those components that enable spacecraft to move while in space.”
Aerojet propulsion systems have helped many of NASA's deep-space probes explore the solar system. Image Credit: NASA.gov
Universe Today:What about in terms of human space flight, when did Aerojet get involved with that?
Van Kleeck: “We first started working on the manned side of the house back during the Gemini Program, from there we progressed to Apollo, then shuttle and we hope to be involved with SLS (Space Launch System) as well.”
Universe Today: I understand that your company also has an extensive history when it comes to unmanned missions as well, care to tell us a bit about that?
Van Kleeck: “We have been on every discovery mission that has ever been launched, we have touched every part of space that you can touch.”
It is Aerojet's solid rocket motors that provide that extra-added “punch” to the versions of the Atlas V launch vehicle that utilize them. Photo Credit: Alan Walters/awaltersphoto.com
Universe Today:Some aerospace companies only produce one product or service, why is Aerojet’s list of offerings so diversified?
Van Kleeck: “We’re quite different than our competitors in that we provide a very wide-range of products to our customers. We’ve provided the liquid engines that went on Titan and now we provide the solids that go on the Atlas V launch vehicle as well as the small chemical and electrical propulsion systems that are utilized on some satellites.”
An Aerojet AJ26 rocket engine is prepared for testing in this image. These engines, as well as a license to produce them, were purchased from Russia and were originally designated the NK-33. Picture Credit: Aerojet
Universe Today:Does this mean that Aerojet places more importance on one space flight system over others?
Van Kleeck: “We view each of the products that we produce as equally important. Having said that, the fact that Aerojet offers a diversity of products and understands each of them well – sets us apart from our competitors. Firms that only produce one type of product tend to work to sell just that one product, whereas Aerojet’s extensive catalog of services allows us to be more objective when offering those services to our customers.”
During a tour of the Vertical Integration Facility, Aerojet's Solid Rocket Motors or SRms -were on full display attached to the Atlas V rocket that is set to send the Mars Science Laboratory rover "Curiosity" to Mars. Photo Credit: Alan Walters/awaltersphoto.com
Universe Today:When you look back, what is one of the most interesting projects that Aerojet has been involved with?
Van Kleeck: “I think as I look back over the past decade, New Horizons comes to mind, it was the first Atlas to launch with five solids on it. I look at that mission in particular as a major accomplish for not just us – but the country as well.”
In this image an AJ26 liquid rocket engine is tested. These engines are utilized as part of Orbital Science's Taurus II program. Photo Credit: Aerojet
Universe Today:What does the future hold for Aerojet?
Van Kleeck: ”We’re working on the Orion crew capsule right now with both liquid propulsion for it as well as solid propulsion for the abort test motor. We’re very much looking forward to seeing Orion fly in the coming years. We are currently putting into place the basic infrastructure to support human space exploration. We are working with both commercial crewed as well as Robert Bigelow to provide propulsion systems that work with their individual system – because no one system fits everyone. We are pleased to be offer systems for a wide variety of space exploration efforts.”
Universe Today:Julie, thanks for taking the time to chat with us today!
Van Kleeck: “No problem at all – it was my pleasure!”
Aerojet’s products will be on full display Nov. 25 as, if everything goes as planned the Mars Science Laboratory (MSL) rover Curiosity is set to launch on that day. Four of the company’s solid rocket motors or SRMs will help power the Curiosity rover on its way to the red planet.
For a taste of what Aerojet’s SRMs provide – please view the NASA video below.
View of Enceladus' surface, image taken October 19, 2011. NASA/JPL-Caltech/Space Science Institute
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Saturn’s tiny moon Enceladus was the centre of attention for the Cassini spacecraft again last week, with beautiful new photos being released of the moon and its water vapour geysers erupting from the south pole. Some views show surface detail on the moon, some are of the geysers themselves and there is a very nice shot of Enceladus silhouetted against Saturn and its rings in the background. There is even a dual ultraviolet stellar occultation in which two of the stars in the belt of the constellation Orion are seen shining through the plumes! Even though these are still raw, unprocessed images, they again capture the beauty of Enceladus and the Saturnian system.
These new images were taken October 19, 2011 during the E-15 flyby, in which Cassini flew about 1,230 kilometres (765 miles) above the surface of Enceladus. The geysers can be seen in the image below, albeit these are not the closest views that Cassini has obtained. Still, it can be clearly seen how far they extend out from the moon, for a few hundred kilometres.
Enceladus and its water vapour geysers, image taken October 19, 2011. Credit: NASA/JPL-Caltech/Space Science Institute
Some surface detail can be seen in the next image below, a hint of the geological complexity of this moon, most notably seen in the “tiger stripe” fissures at the south pole, where the geysers erupt from inside the moon, escaping to the vacuum of space outside, where the water vapour freezes and falls back to the surface of Enceladus as a form of snow. As some have suggested, Enceladus may be a good place for skiing (with the snow being a very fine powder, although the extremely low gravity would probably interfere too much…)!
Enceladus silhouetted against the clouds and rings of Saturn in the background (the rings are edge-on in this view), image taken October 19, 2011. Credit: NASA/JPL-Caltech/Space Science Institute
Having a personal fascination with Enceladus, I was reminded of an older “Captain’s Log” entry on the CICLOPS web site (2006), by Cassini imaging team leader Carolyn Porco, after the initial discovery of the geysers. In part:
“Our detailed analyses of these images have led us to a remarkable conclusion, documented in a paper to be published in the journal SCIENCE tomorrow, that the jets are erupting from pockets of liquid water, possibly as close to the surface as ten meters… a surprising circumstance for a body so small and cold. Other Cassini instruments have found that the fractures on the surface and the plume itself contain simple organic materials, and that there is more heat on average emerging from the south polar terrain, per square meter, than from the Earth.
Gathering all the evidence and steeling ourselves for the “shockwave spread ’round the world”, we find ourselves staring at the distinct possibility that we may have on Enceladus subterranean environments capable of supporting life. We may have just stumbled upon the Holy Grail of modern day planetary exploration. It doesn’t get any more exciting than this.
A great deal more analysis and further exploration with Cassini must ensue before this implication becomes anything more than a suggestion. But at the moment, the prospects are staggering. Enceladus may have just taken center stage as the body in our solar system, outside the Earth, having the most easily accessible bodies of organic-rich water and, hence, significant biological potential.
Many years from now, it may well be that we and those who follow us will look back on these explorations of Saturn and take our discoveries on this otherwise cold little world to be the most wondrous of any we’ve ever made.
Future explorers of Saturn will have much to look forward to.”
And I agree with Cassini imaging team lead Carolyn Porco who said on Twitter of this image: “You’d have to be dead to tire of such magnificent vistas of alien worlds. Eerie Titan, the rings, Pan & Pandora. Glory!”
Titan is the largest in the background, and also the largest moon at 5,150 kilometres (3,200 miles) across, with Dione in front of it, which is 1,123 kilometres (698 miles) in diameter. Just to the right of the edge of the rings is Pandora, which is only about 81 kilometres (50 miles) in diameter. Tiny little Pan, only about 28 kilometres (17 miles) across, can just barely be seen as a speck inside the Encke Gap of the A ring on the left side of the image (look closely!).
Another amazing natural montage showing the alien beauty of the worlds in the Saturnian system. The full-size image can be seen here.
Enceladus and Tethys hang below Saturn's rings in this image from the Cassini spacecraft. Credit: NASA/JPL-Caltech/SS
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Another Cassini stunner! This gorgeous, suitable-for-framing image shows two of Saturn’s moons hanging below the planet’s rings, as if strung on a necklace. Beautiful! Enceladus (504 kilometers, 313 miles across) appears just below the rings, while Tethys (1062 kilometers, 660 miles across) appears below. In this shot, Cassini is also closer to Tethys than Enceladus: the spacecraft is 208,000 kilometers (139,000 miles) from Tethys and 272,000 kilometers (169,000 miles) from Enceladus. This image was taken on September 13, 2011.
See below for some raw images from Cassini’s October 1 close fly by of Enceladus, including a great shot of the moon hovering in front of Saturn’s rings, and a view of the geysers.
A closeup view of Enceladus with Saturn's rings in the background. This raw image was taken on Oct. 1, 2011. Credit: NASA/JPL/Space Science Institute
A view of Enceladus from farther away, with the rings slicing through the view of Saturn in the background. Credit: NASA/JPL/Space Science InstituteA view of the geysers on Enceladus, from Cassini's latest close flyby of the moon, on October 1, 2011.Credit: NASA/JPL/Space Science Institute
Global mosaic of VIMS infrared images acquired during the nominal and equinox Cassini mission. Differences in composition translate into subtle differences of colours in this mosaic, revealing the diversity of terrains on Titan, such as the brownish equatorial dune fields or the bright elevated terrains. (Colour coding : Red=5 um, Green=2.0 um, Blue=1.27 um). Credits JPL/NASA/Univ. of Arizona/CNRS/LPGNantes
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At the University of Nantes, a group of international scientists have been piecing together one of the most amazing jigsaw puzzles of all times… a color image of Saturn’s moon, Titan. For six years the Cassini mission has been busy gathering images and the resulting compilation was presented on October 4 by Stephane Le Mouelic at the 2011 EPSC-DPS Joint Meeting in Nantes, France. While it might not win the Cannes Film Festival, it’s certainly near and dear to an astronomer’s heart…
During the first seventy fly-bys of the famous Saturnian satellite, the Visual and Infrared Mapping Spectrometer (VIMS) gathered imaging records. But sewing together such a large quilt of information wasn’t an easy task. Not only does each image have to be adjusted for differences in lighting conditions, but a pixel-by-pixel match up has to occur to take atmospheric distortions into account. Titan’s methane rain and nitrogen atmosphere isn’t conducive to easy imaging and only a narrow band of infrared wavelengths allow us to take a closer look at the hidden, frozen surface. However, the results have been spectacular and little by little some very “terrestrial” features have come to light.
“As Cassini is orbiting Saturn and not Titan, we can observe Titan only once a month on average. The surface of Titan is therefore revealed year after year, as pieces of the puzzle are progressively put together.” says Le Mouelic. “Deriving a final map with no seams is challenging due to the effects of the atmosphere – clouds, mist etc. – and due to the changing geometries of observation between each flyby.”
Since 2004, Cassini has made 78 fly-bys of the exotic frozen world and another 48 are planned over the next five years. However, VIMS has had very few chances to image Titan with a high spatial resolution. While this still leaves many areas in the proverbial dark, all this can change in the future.
“We have created the maps using low resolution images as a background with the high resolution data on top. In the few opportunities where we have VIMS imagery from the closest approach, we can show details as low as 500 metres per pixel. An example of this is from the 47th flyby, which allowed the observation of the site where the Huygens descent module landed. This observation is a key one as it might help us to bridge the gap between the ground truth provided by Huygens, and ongoing global mapping from orbit, which will continue up to 2017.”
And what does the future hold? Along with updated spatial coverage, the team plans on documenting Titan’s changing seasons from both an atmospheric and surface viewpoint. Changes that are just now beginning to occur.
“Lakes in Titan’s northern hemisphere were first discovered by the RADAR instrument in 2006, appearing as completely smooth areas. However, we had to wait up to June 2010 to obtain the first infrared images of the northern lakes, emerging progressively from the northern winter darkness,” says Le Mouelic. “The infrared observations provide the additional opportunity to investigate the composition of the liquids within the lakes area. Liquid ethane has already been identified by this means.”
Fill ‘er up… We’ll be watching!
Original Story Source: Europlanet News Release. For an even more impressive look, check out the Animation of Titan Mosaic.
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.
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!
