Here’s the May 3, 2012 edition of the Weekly Space Hangout, where we were joined by our usual cast of space journalists, including Alan Boyle, Nicole Gugliucci, Ian O’Neill, Jason Major, Emily Lakdawalla and Fraser Cain. We were then joined by two new people, Amy Shira Teitel from Vintage Space and Sawyer Rosenstein from the Talking Space Podcast.
Want to watch an episode live? We record the Weekly Space Hangout every Thursday at 10:00am PDT, 1:00pm EDT. The live show will appear in Fraser’s Google+ stream, or on our YouTube Channel. You can also watch it live over on Cosmoquest.org.
Enceladus' southern ice geysers are brilliant in backlit sunlight (NASA/JPL/SSI/J. Major)
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The latest images are in from Saturn’s very own personal paparazzi, NASA’s Cassini spacecraft, fresh from its early morning flyby of the ice-spewing moon Enceladus. And, being its last closeup for the next three years, the little moon didn’t disappoint!
The image above is a composite I made from two raw images (this one and this one) assembled to show Enceladus in its crescent-lit entirety with jets in full force. The images were rotated to orient the moon’s southern pole — where the jets originate — toward the bottom.
Cassini was between 72,090 miles (116,000 km) and 90,000 miles (140,000 km) from Enceladus when these images were acquired.
This morning’s E-19 flyby completed a trio of recent close passes by Cassini of the 318-mile (511-km) -wide moon, bringing the spacecraft as low as 46 miles (74 km) above its frozen surface. The goal of the maneuver was to gather data about Enceladus’ internal mass — particularly in the region around its southern pole, where a reservoir of liquid water is thought to reside — and also to look for “hot spots” on its surface that would give more information about its overall energy distribution.
Cassini had previously discovered that Enceladus radiates a surprising amount of heat from its surface, mostly along the “tiger stripe” features — long, deep furrows (sulcae) that gouge its southern hemisphere, they are the source of the water-ice geysers.
Cassini also used the flyby opportunity to study Enceladus’ gravitational field.
By imaging the moon with backlit lighting from the Sun the highly-reflective ice particles in the jets become visible. More direct lighting reduces the jets’ visibility in images, which must be exposed for the natural light of the scene or risk “blowing out” due to Enceladus’ natural high reflectivity.
The images below are raw spacecraft downloads right from the Cassini’s imaging headquarters in Boulder, CO.
Enceladus' geysers in action on May 2, 2012. (NASA/JPL/SSI)Enceladus sprays ice into the hazy E ring, which orbits Saturn (NASA/JPL/SSI)
Cassini also swung closely by Dione during this morning’s flyby but the images from that encounter aren’t available yet. Stay tuned to Universe Today for more postcards from Saturn!
As always, you can follow along with the ongoing Cassini mission on JPL’s dedicated site here, as well as on the Cassini Imaging Central Laboratory for Operations (CICLOPS) site.
Below a darkened Enceladus, a plume of water ice is backlit in this view. Credit: NASA/JPL-Caltech/Space Science Institute
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On May 2, the Cassini spacecraft will be swooping past the moon we all love to love — Enceladus — and coming within 74 kilometers (46 miles) of its fractured, jet-spewing surface. The images should be spectacular, and the science should be just as enticing. With Cassini’s radio science experiment, scientists hope to learn more about how mass is distributed under Enceladus’ south polar region, the very interesting place which features jets of water ice, water vapor and organic compounds spraying out of long fractures.
This is the last close flyby of Enceladus until 2015, so we have to take advantage of the views!
Cassini scientists will be looking specifically for a concentration of mass in that region could indicate subsurface liquid water or an intrusion of warmer-than-average ice that might explain the unusual plume activity. They’ll also be observing the plumes and looking for hot spots to try and understand the global energy balance of Enceladus.
They also hope to learn more about the moon’s internal structure by measuring variations in the gravitational pull of Enceladus against the steady radio link to NASA’s Deep Space Network on Earth.
Additionally, Cassini’s composite infrared spectrometer instrument will be observing the side of Enceladus that always faces away from Saturn to monitor for hot spots. The imaging camera team also plans to take images of the plume to look for variability in the jets.
Cassini will also be flying by Dione at a distance of about 8,000 kilometers (5,000 miles), enabling the imaging cameras to create several mosaic images of the icy moon, and the composite infrared spectrometer to monitor heat emission.
We’ll try to post images and info as they become available!
Cassini's latest view of Enceladus' icy spray, acquired on April 14, 2012.
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Spray it again, Enceladus! This Saturday the Cassini spacecraft paid another visit to Enceladus, Saturn’s 318-mile-wide moon that’s become famous for its icy geysers.During its latest close pass Cassini got a chance to “taste” Enceladus’ spray using its ion and neutral mass spectrometer, giving researchers more information on what sort of watery environment may be hiding under its frozen, wrinkled surface.
The image above shows a diagonal view of Enceladus as seen from the night side. (The moon’s south pole is aimed at a 45-degree angle to the upper right.) Only by imaging the moon backlit by the Sun can the geysers of fine, icy particles be so well seen.
During the flyby Cassini passed within 46 miles (74 km) of Enceladus’ surface.
This image was captured during the closest approach, revealing the distressed terrain of Enceladus’ south pole. Although a bit blurry due to the motion of the spacecraft, boulders can be made out resting along the tops of high , frozen ridges. (Edited from the original raw image to enhance detail.)
Enceladus' southern fissures, the source of its spray. (NASA/JPL/SSI/J. Major)
This flyby occurred less than three weeks after Cassini’s previous visit to Enceladus. Why pay so much attention to one little moon?
Basically, it’s the one place in our solar system that we know of where a world is spraying its “habitable zone” out into space for us to sample.
“More than 90 jets of all sizes near Enceladus’s south pole are spraying water vapor, icy particles, and organic compounds all over the place,” said Carolyn Porco, planetary scientist and Cassini Imaging science team leader, during a NASA interview in March. “Cassini has flown several times now through this spray and has tasted it. And we have found that aside from water and organic material, there is salt in the icy particles. The salinity is the same as that of Earth’s oceans.
“In the end, it’s the most promising place I know of for an astrobiology search,” said Porco. (Read the full interview here.)
A crescent-lit Enceladus sprays its "habitable zone" out into space.
Not to be left out, Tethys was also paid a visit by Cassini. The 662-mile-wide moon boasts one of the most extensively cratered surfaces in the Solar System, tied with its sister moons Rhea and Dione. In this raw image captured by Cassini on April 14, we can see some of the moon’s ancient, larger craters, including Melanthius with its enormous central peak.
Saturn's moon Tethys, imaged by Cassini on April 14, 2012.
Cassini passed Tethys at a distance of about 6,000 miles (9000 km) after departing Enceladus. Cassini’s composite infrared spectrometer looked for patterns in Tethys’ thermal signature while other instruments studied the moon’s geology.
Image credits: NASA/JPL/Space Science Institute. See more images from the Cassini mission on the CICLOPS site here.
Saturn's second-largest moon Rhea, in front of the rings and a blurred Epimetheus (or Janus) whizzing behind. Acquired March 29, 2012.
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Over the past few days NASA’s Cassini spacecraft has performed flybys of several of Saturn’s moons. From the ostentatious Enceladus with its icy geysers to the rugged relief of Rhea, the sharp peaks of Dione’s frigid craters and even diminutive Janus, Cassini has once again returned a stack of stunning views from the Saturnian system, nearly 815 million miles from home.
Check out some of the images, and wish you were there!
110-mile (177-km) -wide Janus in front of Saturn's night side.A crescent-lit Enceladus shows off its jets. (South is up.)Enceladus' fractured surface is some of the most reflective terrain in the Solar System.Wide-angle view of Rhea, Saturn and MimasCrater peak on icy Dione
And here’s a color-composite of Janus I assembled from three raw images taken in ultraviolet, green and infrared color channels. The results were tweaked to make it a little more true-color as what we might see with our limited human vision:
Color composite of Janus in front of Saturn, made from raw images taken in UV, green and IR color filters. (NASA/JPL/SSI/J. Major)
“Though we’ve been in orbit around Saturn for nearly 8 years now, we still continue to image these moons for mapping purposes and, in the case of Enceladus, to learn as much as we can about its famous jets and the subterranean, organic-rich, salty, liquid water chamber from which we believe they erupt.”
– Carolyn Porco, Cassini Imaging Team leader
For more images from Cassini, check out JPL’s mission site and the CICLOPS imaging lab site here.
Cassini image of Enceladus from Dec. 2010 (NASA/JPL/SSI)
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Enceladus, Saturn’s 318-mile-wide moon that’s become famous for its ice-spraying southern jets, is on astronomers’ short list of places in our own solar system where extraterrestrial life could be hiding — and NASA’s Cassini spacecraft is in just the right place to try and sniff it out.
On March 27, Cassini came within 46 miles (74 km) of Enceladus’ south pole, the region where the moon’s many active water-ice jets originate from. This was Cassini’s closest pass yet over the southern pole, allowing the spacecraft to use its ion and neutral mass spectrometer — as well as its plasma spectrometer, recently returned to service — to taste the icy spray emanating from deep fissures called “tiger stripes” that scar Enceladus’ surface.
“More than 90 jets of all sizes near Enceladus’s south pole are spraying water vapor, icy particles, and organic compounds all over the place,” said Carolyn Porco, planetary scientist and Cassini Imaging science team leader. “Cassini has flown several times now through this spray and has tasted it. And we have found that aside from water and organic material, there is salt in the icy particles. The salinity is the same as that of Earth’s oceans.”
In addition to water, salt and organics, there is also a surprising amount of heat — heat generated in part by tidal friction, helping keep Enceladus’ underground water reserves liquid.
“If you add up all the heat, 16 gigawatts of thermal energy are coming out of those cracks,” Porco said.
This creates, in effect, a so-called “Goldilocks zone” of potential habitability orbiting around Saturn… a zone that Cassini has easy access to.
“It’s erupting out into space where we can sample it. It sounds crazy but it could be snowing microbes on the surface of this little world,” Porco said. “In the end, it’s the most promising place I know of for an astrobiology search. We don’t even need to go scratching around on the surface. We can fly through the plume and sample it. Or we can land on the surface, look up and stick our tongues out. And voilà…we have what we came for.”
Cassini's view down into a jetting "tiger stripe" in August 2010
Cassini’s latest results — and images! — from the flyby should be landing on Earth any time now. Stay tuned to Universe Today for more updates on Cassini and Enceladus.
Color-composite image from Cassini raw data acquired on March 12, 2012. (NASA/JPL/SSI/J. Major)
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Little Enceladus and enormous Titan are seen on either side of Saturn’s rings in this image, a color-composite made from raw images acquired by Cassini on March 12, 2012. The original images were taken in red, green and blue color channels, and with a little Photoshop editing I combined them into a roughly true-color view of what Cassini saw as it passed within 1,045,591 km of Enceladus.
Along with Jupiter’s moon Europa, a tiny Saturnian moon, Enceladus, has become one of the most fascinating places in the solar system and a prime target in the search for extraterrestrial life. Its outward appearance is that of a small, frozen orb, but it revealed some surprises when the Cassini spacecraft gave us our first ever close-up look at this little world – huge geysers of water vapour spewing from its south pole. The implications were thought-provoking: Enceladus, like Europa, may have an ocean of liquid water below the surface. Unlike Europa however, the water is apparently able to make it up to the surface via fissures, erupting out into space as giant plumes.
Now, a new project sponsored by the German Aerospace Center, Enceladus Explorer, was launched on February 22, 2012, in an attempt to answer the question of whether there could be life on (or rather, inside) Enceladus. The project lays the groundwork for a new, ambitious mission being proposed for some time in the future.
Cassini was able to sample some of the plumes directly during its closest approaches to the moon, revealing that they contain water vapour, ice particles and organic molecules. If they originate from a reservoir of subsurface liquid water, as now thought by most scientists involved, it would indicate an environment which could be ideal for life to have started. The necessary ingredients for life (as we know it at least) are all there – water, heat and organic material. The fissures themselves generate much more heat relatively than the surrounding surface, suggesting that the conditions below the surface are much warmer. Maybe not “hot” per se, but warm enough, perhaps also with the aid of salts like in Earth’s oceans, to keep the water liquid.
But what is the best way to search for evidence of life there? Follow-up missions have been proposed, to again sample the plumes, but with instruments able to look for life itself, which Cassini can’t do. This would seem ideal, as the water is being spewed out into space, with no drilling through the ice necessary. But the Enceladus Explorer project is proposing to do just that; the rationale is that any organisms (most likely microscopic) which may be in the water could easily be destroyed by the force of the ejection from the fissure. So then what is the best way to sample the water itself down below?
Enceladus Explorer would place a base station on the surface near one of the fissures; an ice drilling probe, the IceMole, would then melt its way through the ice crust to a depth of 100-200 metres until it reaches a liquid water reservoir. It would obtain samples of the water and examine them in situ for any traces of microorganisms. With no GPS system available, or external reference points to use, the probe would need to function autonomously, finding its own way through the ice to the water below.
The IceMole is already being tested here on Earth, and has successfully melted its way through the ice of the Morteratsch glacier in Switzerland. The next experiment will have it navigate its way through ice in the Antarctic, sampling completely uncontaminated water from a subsurface lake below the ice, much like the conditions found on Enceladus.
There is no timeframe yet for such a mission, especially given current budgets, but the Enceladus Explorer project has already shown that it is certainly technologically feasible and would provide an incredible look at an environment in the outer solar system which is amazingly Earth-like yet utterly alien at the same time.
Discovered by the Cassini mission, Saturn Kilometric Radiation (SKR) has been something of an enigma to astronomers. According to the radio and plasma wave instruments, variations occur in sync with the planet’s rotation. However, there are periodic “bursts” of radiation which are in line with Saturn’s magnetosphere. What makes this odd? The rate isn’t quite the same.
Thanks to investigations of Enceladus by Cassini in 2008, new information about the plasma environment surrounding Saturn’s satellite could show a marked impact on the magnetosphere. This image and video show a changing pattern of radio waves from Saturn known as Saturn Kilometric Radiation, as detected by NASA’s Cassini spacecraft. The colors indicate the emitted power of the radio waves, with red as the strongest.
How is it being affected? Thanks to Enceladus’ “spraying” nature, the huge plume of water vapor and ice from its southern pole provides a hefty source of plasma to feed Saturn’s magnetosphere and E-Ring. These negatively charged particles are again impacting the motion of the localized plasma.
“These signatures result from half or more of the electrons being attached to dust grains and by the interaction between the surrounding cold plasma and the predominantly negatively charged submicrometer-sized dust grains.” says M. W. Morooka (et al). “The dust and plasma properties estimated from the observations clearly show that the dust-plasma interaction is collective.”
According to the AGU Journal, this dust-plasma interaction impacts the dynamics of Saturn’s magnetosphere, possibly influencing the rate of SKR emissions.
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.
