Orbiter-Forum  

Go Back   Orbiter-Forum > Far Side of the Moon > Spaceflight News
Register Blogs Orbinauts List Social Groups FAQ Projects Mark Forums Read

Spaceflight News Share news, stories, or discussions about government and private spaceflight programs; including ESA, ISS, NASA, Russian Space Program, Virgin Galactic, & more!

Reply
 
Thread Tools
Old 04-21-2011, 10:07 AM   #46
orb
O-F Administrator
Ninja
 
orb's Avatar

Default

NASA / NASA JPL:
Cassini Sees Saturn Electric Link With Enceladus

April 20, 2011

PASADENA, Calif. -- NASA is releasing the first images and sounds of an electrical connection between Saturn and one of its moons, Enceladus. The data collected by the agency's Cassini spacecraft enable scientists to improve their understanding of the complex web of interaction between the planet and its numerous moons. The results of the data analysis are published in the journals Nature

Scientists previously theorized an electrical circuit should exist at Saturn. After analyzing data that Cassini collected in 2008, scientists saw a glowing patch of ultraviolet light emissions near Saturn's north pole that marked the presence of a circuit, even though the moon is 240,000 kilometers (150,000 miles) away from the planet.

Click on images for details
Electrical Circuit Between Saturn and Enceladus
NASA's Cassini spacecraft has spotted a glowing patch of ultraviolet light near Saturn's north pole that marks the presence of an electrical circuit that connects Saturn with its moon Enceladus.
-
Image credit: NASA/JPL/University of Colorado/Central Arizona College
Enceladus 'Footprint' on Saturn
This artist's concept shows a glowing patch of ultraviolet light near Saturn's north pole that occurs at the "footprint" of the magnetic connection between Saturn and its moon Enceladus.
-
Credit: NASA/JPL/JHUAPL/University of Colorado/Central Arizona College/SSI


The patch occurs at the end of a magnetic field line connecting Saturn and its moon Enceladus. The area, known as an auroral footprint, is the spot where energetic electrons dive into the planet's atmosphere, following magnetic field lines that arc between the planet's north and south polar regions.

"The footprint discovery at Saturn is one of the most important fields and particle revelations from Cassini and ultimately may help us understand Saturn's strange magnetic field," said Marcia Burton, a Cassini fields and particles scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "It gives us the first visual connection between Saturn and one of its moons."

Click on images to view videos
Hiss from Aurora Caused by Enceladus
This video demonstrates the hiss-like radio noise generated by electrons moving along magnetic field lines from the Saturnian moon Enceladus to a glowing patch of ultraviolet light on Saturn.
-
Image credit: NASA/JPL/University of Iowa
Saturn and Enceladus Electrical Link
This animated graphic shows how Saturn and its moon Enceladus are electrically linked. Magnetic field lines, invisible to the human eye but detectable by the fields and particles instruments on NASA’s Cassini spacecraft, arc from Saturn’s north polar region to south polar region.
-
Image credit: NASA/JPL/University of Iowa


The auroral footprint measures approximately 1,200 kilometers (750 miles) by less than 400 kilometers (250 miles), covering an area comparable to California or Sweden. At its brightest, the footprint shone with an ultraviolet light intensity far less than Saturn's polar auroral rings, but comparable to the faintest aurora visible at Earth without a telescope in the visible light spectrum. Scientists have not found a matching footprint at the southern end of the magnetic field line.
Jupiter's active moon Io creates glowing footprints near Jupiter's north and south poles, so scientists suspected there was an analogous electrical connection between Saturn and Enceladus. It is the only known active moon in the Saturn system with jets spraying water vapor and organic particles into space. For years, scientists used space telescopes to search Saturn's poles for footprints, but they found none.

"Cassini fields and particles instruments found particle beams aligned with Saturn's magnetic field near Enceladus, and scientists started asking if we could see an expected ultraviolet spot at the end of the magnetic field line on Saturn," said Wayne Pryor, a lead author of the Nature study released today, and Cassini co-investigator at Central Arizona College in Coolidge, Ariz. "We were delighted to find the glow close to the 'bulls-eye' at the center of our target."

Click on image for video
Movie of Enceladus 'Footprint' on Saturn
NASA's Cassini spacecraft has spotted a glowing patch of ultraviolet light near Saturn's north pole that marks the presence of an electrical circuit that connects Saturn with its moon Enceladus.
-
Image Credit: NASA/JPL/University of Colorado/Central Arizona College


In 2008, Cassini detected a beam of energetic protons near Enceladus aligned with the magnetic field and field-aligned electron beams. A team of scientists analyzed the data and concluded the electron beams had sufficient energy flux to generate a detectable level of auroral emission at Saturn. A few weeks later, Cassini captured images of an auroral footprint in Saturn's northern hemisphere. In 2009, a group of Cassini scientists led by Donald Gurnett at the University of Iowa in Iowa City, detected more complementary signals near Enceladus consistent with currents that travel from the moon to the top of Saturn's atmosphere, including a hiss-like sound from the magnetic connection. That paper was published in March in Geophysical Research Letters.

The water cloud above the Enceladus jets produces a massive, ionized "plasma" cloud through its interactions with the magnetic bubble around Saturn. This cloud disturbs the magnetic field lines. The footprint appears to flicker in these new data, so the rate at which Enceladus is spewing particles may vary.

"The new data are adding fuel to the fire of some long-standing debates about this active little moon," said Abigail Rymer, the other lead author of the Nature study and a Cassini team scientist based at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. "Scientists have been wondering whether the venting rate is variable, and these new data suggest that it is."

{...}




NASA JPL - Cassini Solstice:NASA: Cassini Probe Sees Electric Link With Saturn And One Of Its Moons

SPACE.com: Icy Moon Creates Extra Northern Lights on Saturn
orb is offline   Reply With Quote
Old 05-20-2011, 09:56 AM   #47
orb
O-F Administrator
Ninja
 
orb's Avatar

Default

NASA / NASA JPL:
Cassini and Telescope See Violent Saturn Storm

May 19, 2011

PASADENA, Calif. -- NASA's Cassini spacecraft and a European Southern Observatory ground-based telescope tracked the growth of a giant early-spring storm in Saturn's northern hemisphere that is so powerful it stretches around the entire planet. The rare storm has been wreaking havoc for months and shooting plumes of gas high into the planet's atmosphere.

Cassini's radio and plasma wave science instrument first detected the large disturbance, and amateur astronomers tracked its emergence in December 2010. As it rapidly expanded, its core developed into a giant, powerful thunderstorm. The storm produced a 3,000-mile-wide (5,000-kilometer-wide) dark vortex, possibly similar to Jupiter's Great Red Spot, within the turbulent atmosphere.

Click on images for details
Thermal infrared images of Saturn from the Very Large Telescope Imager and Spectrometer for the mid-Infrared (VISIR) instrument on the European Southern Observatory's Very Large Telescope, on Cerro Paranal, Chile, appear at center and on the right. Image credit: ESO/Univ. of Oxford/T. Barry
This false-color infrared image, obtained by NASA's Cassini spacecraft, shows clouds of large ammonia ice particles dredged up by a powerful storm in Saturn's northern hemisphere. Image credit: NASA/JPL/Univ. of Arizona
Measurements by NASA's Cassini spacecraft reveal temperatures in a high layer of Saturn's atmosphere known as the stratosphere and show the dramatic effects of the massive storm deep below. Image credit: NASA/JPL/GSFC/Univ. Oxford


The dramatic effects of the deep plumes disturbed areas high up in Saturn's usually stable stratosphere, generating regions of warm air that shone like bright "beacons" in the infrared. Details are published in this week's edition of Science Magazine.

"Nothing on Earth comes close to this powerful storm," says Leigh Fletcher, the study's lead author and a Cassini team scientist at the University of Oxford in the United Kingdom. "A storm like this is rare. This is only the sixth one to be recorded since 1876, and the last was way back in 1990."

This is the first major storm on Saturn observed by an orbiting spacecraft and studied at thermal infrared wavelengths, where Saturn's heat energy reveals atmospheric temperatures, winds and composition within the disturbance.

Temperature data were provided by the Very Large Telescope (VLT) on Cerro Paranal in Chile and Cassini's composite infrared spectrometer (CIRS), operated by NASA's Goddard Space Flight Center in Greenbelt, Md.

"Our new observations show that the storm had a major effect on the atmosphere, transporting energy and material over great distances, modifying the atmospheric winds -- creating meandering jet streams and forming giant vortices -- and disrupting Saturn's slow seasonal evolution," said Glenn Orton, a paper co-author, based at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

The violence of the storm -- the strongest disturbances ever detected in Saturn's stratosphere -- took researchers by surprise. What started as an ordinary disturbance deep in Saturn's atmosphere punched through the planet's serene cloud cover to roil the high layer known as the stratosphere.

"On Earth, the lower stratosphere is where commercial airplanes generally fly to avoid storms which can cause turbulence," says Brigette Hesman, a scientist at the University of Maryland in College Park who works on the CIRS team at Goddard and is the second author on the paper. "If you were flying in an airplane on Saturn, this storm would reach so high up, it would probably be impossible to avoid it."

Other indications of the storm's strength are the changes in the composition of the atmosphere brought on by the mixing of air from different layers. CIRS found evidence of such changes by looking at the amounts of acetylene and phosphine, both considered to be tracers of atmospheric motion. A separate analysis using Cassini's visual and infrared mapping spectrometer, led by Kevin Baines of JPL, confirmed the storm is very violent, dredging up larger atmospheric particles and churning up ammonia from deep in the atmosphere in volumes several times larger than previous storms. Other Cassini scientists are studying the evolving storm, and a more extensive picture will emerge soon.

{...}
orb is offline   Reply With Quote
Thanked by:
Old 06-16-2011, 03:40 AM   #48
orb
O-F Administrator
Ninja
 
orb's Avatar

Default

NASA / NASA JPL:
Plasma Spectrometer Operations on Hold

June 15, 2011

PASADENA, Calif. – Mission managers for NASA's Cassini spacecraft suspended operation of the Cassini plasma spectrometer instrument on Tuesday, June 14, 2011, after a series of voltage shifts on the spacecraft. They will determine when the instrument can resume collecting data.

The Cassini spacecraft is designed to operate with a "balanced" voltage source to create a tolerance to short circuits. On May 1, a voltage shift occurred, most likely explained by a short circuit happening somewhere in the system. On June 11, a voltage shift in the opposite direction occurred, indicating an additional short circuit. In both cases, all instruments and engineering subsystems continued to operate properly.

Analysis of telemetry data from the spacecraft by the engineering team pointed to the Cassini plasma spectrometer instrument as the cause of the voltage shifts. The instrument has additional capacitors in the power lines for noise reduction. The concern was that one or more of these capacitors may have short-circuited, which would cause the voltage to shift and explain the observed changes. Although the instrument was operating properly, engineers decided to turn it off as a precaution until the events could be better understood.

The suspension of the plasma spectrometer operations is not expected to affect other science data gathering or navigation. The plan is to resume normal plasma spectrometer operations after further analysis is completed to understand the cause of the issue better.

{...}
orb is offline   Reply With Quote
Thanked by:
Old 06-20-2011, 05:11 PM   #49
orb
O-F Administrator
Ninja
 
orb's Avatar

Default

NASA / NASA JPL:
Cassini Captures Ice Queen Helene

June 20, 2011

NASA's Cassini spacecraft has successfully completed its second-closest encounter with Saturn's icy moon Helene, beaming down raw images of the small moon. At closest approach, on June 18, Cassini flew within 4,330 miles (6,968 kilometers) of Helene's surface. It was the second closest approach to Helene of the entire mission.

Click on images for details
NASA's Cassini spacecraft obtained this unprocessed image of Saturn's moon Helene on June 18, 2011.
Image credit: NASA/JPL-Caltech/Space Science Institute
NASA's Cassini spacecraft obtained this unprocessed image of Saturn's moon Helene on June 18, 2011.
Image credit: NASA/JPL-Caltech/Space Science Institute
NASA's Cassini spacecraft obtained this unprocessed image of Saturn's moon Helene on June 18, 2011.
Image credit: NASA/JPL-Caltech/Space Science Institute


Cassini passed from Helene's night side to the moon's sunlit side. It also captured images of the Saturn-facing side of the moon in sunlight, a region that was only illuminated by sunlight reflected off Saturn the last time Cassini was close, in March 2010. This flyby will enable scientists to finish creating a global map of Helene, so they can better understand the history of impacts to the moon and gully-like features seen on previous flybys.

The closest Helene encounter of the mission took place on March 10, 2010, when Cassini flew within 1,131 miles (1,820 kilometers) of the moon.

The latest raw images are online at: http://saturn.jpl.nasa.gov/photos/raw/.

{...}
orb is offline   Reply With Quote
Thanked by:
Old 06-22-2011, 05:27 PM   #50
orb
O-F Administrator
Ninja
 
orb's Avatar

Default

NASA / NASA JPL:
Cassini Captures Ocean-Like Spray at Saturn Moon

June 22, 2011

PASADENA, Calif. -- NASA's Cassini spacecraft has discovered the best evidence yet for a large-scale saltwater reservoir beneath the icy crust of Saturn's moon Enceladus. The data came from the spacecraft's direct analysis of salt-rich ice grains close to the jets ejected from the moon.

Click on image for details
Dramatic plumes, both large and small, spray water ice out from many locations along the famed "tiger stripes" near the south pole of Saturn's moon Enceladus. The tiger stripes are fissures that spray icy particles, water vapor and organic compounds.
Image credit: NASA/JPL/Space Science Institute


Data from Cassini's cosmic dust analyzer show the grains expelled from fissures, known as tiger stripes, are relatively small and predominantly low in salt far away from the moon. But closer to the moon's surface, Cassini found that relatively large grains rich with sodium and potassium dominate the plumes. The salt-rich particles have an "ocean-like" composition and indicate that most, if not all, of the expelled ice and water vapor comes from the evaporation of liquid salt water. The findings appear in this week's issue of the journal Nature.

"There currently is no plausible way to produce a steady outflow of salt-rich grains from solid ice across all the tiger stripes other than salt water under Enceladus's icy surface," said Frank Postberg, a Cassini team scientist at the University of Heidelberg, Germany, and the lead author on the paper. When water freezes, the salt is squeezed out, leaving pure water ice behind. If the plumes emanated from ice, they should have very little salt in them.

The Cassini mission discovered Enceladus' water-vapor and ice jets in 2005. In 2009, scientists working with the cosmic dust analyzer examined some sodium salts found in ice grains of Saturn's E ring, the outermost ring that gets its material primarily from Enceladean jets. But the link to subsurface salt water was not definitive.

The new paper analyzes three Enceladus flybys in 2008 and 2009 with the same instrument, focusing on the composition of freshly ejected plume grains. The icy particles hit the detector target at speeds between 15,000 and 39,000 mph (23,000 and 63,000 kilometers per hour), vaporizing instantly. Electrical fields inside the cosmic dust analyzer separated the various constituents of the impact cloud.

The data suggest a layer of water between the moon's rocky core and its icy mantle, possibly as deep as about 50 miles (80 kilometers) beneath the surface. As this water washes against the rocks, it dissolves salt compounds and rises through fractures in the overlying ice to form reserves nearer the surface. If the outermost layer cracks open, the decrease in pressure from these reserves to space causes a plume to shoot out. Roughly 400 pounds (200 kilograms) of water vapor is lost every second in the plumes, with smaller amounts being lost as ice grains. The team calculates the water reserves must have large evaporating surfaces, or they would freeze easily and stop the plumes.

"This finding is a crucial new piece of evidence showing that environmental conditions favorable to the emergence of life can be sustained on icy bodies orbiting gas giant planets," said Nicolas Altobelli, the European Space Agency's project scientist for Cassini.

Cassini's ultraviolet imaging spectrograph also recently obtained complementary results that support the presence of a subsurface ocean. A team of Cassini researchers led by Candice Hansen of the Planetary Science Institute in Tucson, Ariz., measured gas shooting out of distinct jets originating in the moon's south polar region at five to eight times the speed of sound, several times faster than previously measured. These observations of distinct jets, from a 2010 flyby, are consistent with results showing a difference in composition of ice grains close to the moon's surface and those that made it out to the E ring. That paper was published in the June 9 issue of Geophysical Research Letters.

"Without an orbiter like Cassini to fly close to Saturn and its moons -- to taste salt and feel the bombardment of ice grains -- scientists would never have known how interesting these outer solar system worlds are," said Linda Spilker, NASA's Cassini project scientist at the Jet Propulsion Laboratory in Pasadena, Calif.

{...}



ESA:
Cassini samples the icy spray of Enceladus' water plumes

Click on images for larger versions
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. The 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 of the moon. This enhanced and false-coloured image shows the enormous extent of the fainter, larger-scale component of the plume.
Credits: NASA/JPL/Space Science Institute
Jets of icy particles bursting from Saturn's moon Enceladus are shown in this NASA/ESA/ASI Cassini image taken on 27 November 2005. This and other recent images of Enceladus backlit by the Sun show the fountain-like sprays of the fine material that tower 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 of the moon.
Credits: NASA/JPL/Space Science Institute
orb is offline   Reply With Quote
Old 07-06-2011, 06:57 PM   #51
orb
O-F Administrator
Ninja
 
orb's Avatar

Default

NASA / NASA JPL:
Cassini Captures Images and Sounds of Saturn Storm

July 06, 2011

PASADENA, Calif. -- Scientists analyzing data from NASA's Cassini spacecraft now have the first-ever, up-close details of a Saturn storm that is eight times the surface area of Earth.

On Dec. 5, 2010, Cassini first detected the storm that has been raging ever since. It appears approximately 35 degrees north latitude of Saturn. Pictures from Cassini's imaging cameras show the storm wrapping around the entire planet covering approximately 2 billion square miles (4 billion square kilometers).

The storm is about 500 times larger than the biggest storm previously seen by Cassini during several months from 2009 to 2010. Scientists studied the sounds of the new storm's lightning strikes and analyzed images taken between December 2010 and February 2011. Data from Cassini's radio and plasma wave science instrument showed the lightning flash rate as much as 10 times more frequent than during other storms monitored since Cassini's arrival to Saturn in 2004. The data appear in a paper published this week in the journal Nature.

"Cassini shows us that Saturn is bipolar," said Andrew Ingersoll, an author of the study and a Cassini imaging team member at the California Institute of Technology in Pasadena, Calif. "Saturn is not like Earth and Jupiter, where storms are fairly frequent. Weather on Saturn appears to hum along placidly for years and then erupt violently. I'm excited we saw weather so spectacular on our watch."

At its most intense, the storm generated more than 10 lightning flashes per second. Even with millisecond resolution, the spacecraft's radio and plasma wave instrument had difficulty separating individual signals during the most intense period. Scientists created a sound file from data obtained on March 15 at a slightly lower intensity period.

Click on images for details
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
These false-color images from NASA's Cassini spacecraft chronicle a day in the life of a huge storm that developed from a small spot that appeared 12 weeks earlier in Saturn's northern mid-latitudes.
Image credit: NASA/JPL-Caltech/SSI
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

Cassini has detected 10 lightning storms on Saturn since the spacecraft entered the planet's orbit and its southern hemisphere was experiencing summer, with full solar illumination not shadowed by the rings. Those storms rolled through an area in the southern hemisphere dubbed "Storm Alley." But the sun's illumination on the hemispheres flipped around August 2009, when the northern hemisphere began experiencing spring.

"This storm is thrilling because it shows how shifting seasons and solar illumination can dramatically stir up the weather on Saturn," said Georg Fischer, the paper's lead author and 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."

The storm's results are the first activities of a new "Saturn Storm Watch" campaign. During this effort, Cassini looks at likely storm locations on Saturn in between its scheduled observations. On the same day that the radio and plasma wave instrument detected the first lightning, Cassini's cameras happened to be pointed at the right location as part of the campaign and captured an image of a small, bright cloud. Because analysis on that image was not completed immediately, Fischer sent out a notice to the worldwide amateur astronomy community to collect more images. A flood of amateur images helped scientists track the storm as it grew rapidly, wrapping around the planet by late January 2011.

The new details about this storm complement atmospheric disturbances described recently by scientists using Cassini's composite infrared spectrometer and the European Southern Observatory's Very Large Telescope. The storm is the biggest observed by spacecraft orbiting or flying by Saturn. NASA's Hubble Space Telescope captured images in 1990 of an equally large storm.

{...}




NASA Press Release: RELEASE : 11-220 - Cassini Spacecraft Captures Images And Sounds Of Big Saturn Storm
orb is offline   Reply With Quote
Thanked by:
Old 08-09-2011, 12:14 AM   #52
orb
O-F Administrator
Ninja
 
orb's Avatar

Default

NASA / NASA JPL:
Putting it all Together on Titan

August 08, 2011

Three of Titan's major surface features -- dunes, craters and the enigmatic Xanadu -- appear in this radar image from NASA's Cassini spacecraft. The hazy, bright area at the left that extends to the lower center of the image marks the northwest edge of Xanadu, a 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 between these two features are linear dunes, similar to sand dunes on Earth in Egypt and Namibia.

Click on image for details
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


The image was taken by Cassini's Titan Radar Mapper on June 21, 2011.

{...}

For more information, see: http://saturn.jpl.nasa.gov/photos/im...m?imageId=4338.



NASA JPL: Catalog page for the "PIA14500: Titan: Putting it all Together" image
orb is offline   Reply With Quote
Thanked by:
Old 08-26-2011, 07:20 PM   #53
orb
O-F Administrator
Ninja
 
orb's Avatar

Default

NASA / NASA JPL:
Cassini Closes in on Saturn's Tumbling Moon Hyperion

August 26, 2011

NASA's Cassini spacecraft captured new views of Saturn's oddly shaped moon Hyperion during its encounter with this cratered body on Thursday, Aug. 25. Raw images were acquired as the spacecraft flew past the moon at a distance of about 15,500 miles (25,000 kilometers), making this the second closest encounter.

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


Hyperion is a small moon -- just 168 miles (270 kilometers) across. It has an irregular shape and surface appearance, and it rotates chaotically as it tumbles along in orbit. This odd rotation prevented scientists from predicting exactly what terrain the spacecraft's cameras would image during this flyby.

However, 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.

The latest raw images of Hyperion are online at: http://saturn.jpl.nasa.gov/photos/raw/.

Cassini's closest encounter with Hyperion was on September 26, 2005, when the spacecraft flew approximately 310 miles (500 kilometers) above the moon's surface.
Cassini's next flyby of Hyperion will be on Sept. 16, 2011, when it passes the tumbling moon at a distance of about 36,000 miles (58,000 kilometers).

{...}
orb is offline   Reply With Quote
Thanked by:
Old 09-17-2011, 12:53 AM   #54
orb
O-F Administrator
Ninja
 
orb's Avatar

Default

NASA / NASA JPL:
Cassini Presents Saturn Moon Quintet

September 16, 2011

With the artistry of a magazine cover shoot, NASA's Cassini spacecraft captured this portrait of five of Saturn's moons poised along the planet's rings.

Click on image for details
NASA's Cassini spacecraft captures five of Saturn's moons in one image: Janus, Pandora, Enceladus, Mimas and Rhea.
Image credit: NASA/JPL-Caltech/Space Science Institute


From left to right are Janus, Pandora, Enceladus, Mimas and finally Rhea, bisected by the right side of the frame. The view was acquired at a distance of approximately 684,000 miles (1.1 million kilometers) from Rhea and 1.1 million miles (1.8 million kilometers) from Enceladus.

The image was taken in visible green light with the Cassini spacecraft narrow-angle camera on July 29, 2011. Image scale is about 4 miles (7 kilometers) per pixel on Rhea and 7 miles (11 kilometers) per pixel on Enceladus.

{...}
orb is offline   Reply With Quote
Old 09-21-2011, 05:19 PM   #55
orb
O-F Administrator
Ninja
 
orb's Avatar

Default

NASA / NASA JPL:
Saturn's Moon Enceladus Spreads Its Influence

September 21, 2011

Chalk up one more feat for Saturn's intriguing moon Enceladus. The small, dynamic moon spews out dramatic plumes of water vapor and ice -- first seen by NASA's Cassini spacecraft in 2005. It possesses simple organic particles and may house liquid water beneath its surface. Its geyser-like jets create a gigantic halo of ice, dust and gas around Enceladus that helps feed Saturn's E ring. Now, thanks again to those icy jets, Enceladus is the only moon in our solar system known to influence substantially the chemical composition of its parent planet.

Click on image to enlarge
Water vapor and ice erupt from Saturn's moon Enceladus, the source of a newly discovered donut-shaped cloud around Saturn.
Image credit: NASA/JPL-Caltech/Space Science Institute


In June, the European Space Agency announced that its Herschel Space Observatory, which has important NASA contributions, had found a huge donut-shaped cloud, or torus, of water vapor created by Enceladus encircling Saturn. The torus is more than 373,000 miles (600,000 kilometers) across and about 37,000 miles (60,000 kilometers) thick. It appears to be the source of water in Saturn's upper atmosphere.

Though it is enormous, the cloud had not been seen before because water vapor is transparent at most visible wavelengths of light. But Herschel could see the cloud with its infrared detectors. "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, Calif.

The discovery of the torus around Saturn did not come as a complete surprise. NASA's Voyager and Hubble missions had given scientists hints of the existence of water-bearing clouds around Saturn. Then in 1997, the European Space Agency's Infrared Space Observatory confirmed the presence of water in Saturn's upper atmosphere. NASA's Submillimeter Wave Astronomy Satellite also observed water emission from Saturn at far-infrared wavelengths in 1999.

While a small amount of gaseous water is locked in the warm, lower layers of Saturn's atmosphere, it can't rise to the colder, higher levels. To get to the upper atmosphere, water molecules must be entering Saturn's atmosphere from somewhere in space. But from where and how? Those were mysteries until now.

Build the model and the data will come.

The answer came by combining Herschel's observations of the giant cloud of water vapor created by Enceladus' plumes with computer models that researchers had already been developing to describe the behavior of water molecules in clouds around Saturn.

One of these researchers is 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. "What's amazing is that the model," said Cassidy, "which is one iteration in a long line of cloud models, was built without knowledge of the observation. 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."

The results show that, though most of the water in the torus is lost to space, some of the water molecules fall and freeze on Saturn's rings, while a small amount -- about 3 to 5 percent -- gets through the rings to Saturn's atmosphere. This is just enough to account for the water that has been observed there.

Herschel's measurements combined with the cloud models also provided new information about the rate at which water vapor is erupting out of the dark fractures, known as "tiger stripes," on Enceladus' southern polar region. Previous measurements by the Ultraviolet Imaging Spectrograph (UVIS) instrument aboard the Cassini spacecraft showed that every second the moon is ejecting about 440 pounds (200 kilograms) of water vapor.

"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."

While a small fraction of the water molecules inside the torus end up in Saturn's atmosphere, most are broken down into separate atoms of 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."

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

{...}
orb is offline   Reply With Quote
Old 10-04-2011, 12:03 AM   #56
orb
O-F Administrator
Ninja
 
orb's Avatar

Default

NASA / NASA JPL:
Saturn's Geyser Moon Enceladus Shows off for NASA's Cassini

October 03, 2011

PASADENA, Calif. -- NASA's Cassini spacecraft successfully completed its Oct. 1 flyby of Saturn's moon Enceladus and its jets of water vapor and ice. At its closest approach, the spacecraft flew approximately 62 miles (100 kilometers) above the moon's surface. The close approach was designed to give some of Cassini's instruments, including the ion and neutral mass spectrometer, the chance to "taste" the jets themselves.

At a higher vantage point during the encounter, Cassini's high-resolution camera captured pictures of the jets emanating from the moon's south polar region. The latest raw images of Enceladus are online at: http://saturn.jpl.nasa.gov/photos/raw/.

Click on images to enlarge
Cassini sees jets of water vapor and ice from Enceladus.
Image credit: NASA/JPL-Caltech/Space Science Institute
During Cassini's Oct. 1, 2011 flyby, Saturn's moon Enceladus was in full view.
Image credit: NASA/JPL-Caltech/Space Science Institute
NASA's Cassini imaged Enceladus' surface during its Oct. 1, 2011 flyby.
Image credit: NASA/JPL-Caltech/Space Science Institute


The images of the surface include previously seen leading-hemisphere terrain. However, during this encounter, multi-spectral imaging of these terrains extended farther into the ultraviolet region of the electromagnetic spectrum than had previously been achieved at this resolution. By looking at the surface at ultraviolet wavelengths, scientists can better detect the difference between surface materials and shadows than they can at visible wavelengths, where icy materials are highly reflective and shadows are washed out. With both ultraviolet and visible images of the same terrain available to them, scientists will better understand how the surface coverage of icy particles coming from the vents and plumes changes with terrain type and age.

Cassini's next pass of this fascinating moon will be Oct. 19, when the spacecraft flies by at an altitude of approximately 765 miles (1231 kilometers).

{...}




Discovery News: Cassini Buzzes Cracked and Cratered Enceladus
orb is offline   Reply With Quote
Old 10-19-2011, 12:55 AM   #57
orb
O-F Administrator
Ninja
 
orb's Avatar

Default

NASA / NASA JPL:
Orion's Belt Lights Up Cassini's View of Enceladus

October 18, 2011

NASA's Cassini mission will take advantage of the position of two of the three stars in Orion's belt when the spacecraft flies by Saturn's moon Enceladus on Wed., Oct. 19. As the hot, bright stars pass behind the moon's icy jets, Cassini's ultraviolet imaging spectrograph will acquire a two-dimensional view of these dramatic plumes of water vapor and icy material erupting from the moon's southern polar region. This flyby is the mission's first-ever opportunity to probe the jets with two stars simultaneously, a dual stellar occultation.

Click on image for details
Dramatic plumes, both large and small, spray water ice out from many locations along the famed "tiger stripes" near the south pole of Saturn's moon Enceladus.
Image credit: NASA/JPL/SSI


From Cassini's viewpoint, the closest of Orion's stars will appear about 9 miles (15 kilometers) above the moon's limb, or outer edge. The second star will appear higher, about 19 miles (30 kilometers) from the limb. In the foreground will be Enceladus' icy plumes, which extend hundreds of miles into space.

As the spacecraft passes Enceladus, its infrared instruments, cameras and other instruments will also be monitoring activity on the moon. The orbiter will fly within about 765 miles (1,230 kilometers) of Enceladus' surface.

This flyby will provide researchers with new insight into the jets--their content, the speed at which they are travelling and how they vary. It will also provide new information on the famed "tiger stripes" from which the jets erupt. These fissures in Enceladus' surface are the "nozzles" from which the plumes are propelled at supersonic speeds. Knowing more about their structure may help unlock some of the secrets within Enceladus' interior, including the source of the water-rich plumes.

The Cassini mission celebrated the 14th anniversary of the spacecraft's launch last week.
Having completed its four-year prime mission in 2008, the mission is now on its second extension, the Cassini Solstice Mission. One of the mission's goals is to provide further information on previous Cassini discoveries, such as lakes on Titan and plumes on Enceladus, first detected by Cassini in 2005.

{...}

More information on the Enceladus flyby, called "E15," is available at: http://saturn.jpl.nasa.gov/mission/f...ladus20111019/
orb is offline   Reply With Quote
Thanked by:
Old 10-20-2011, 08:07 PM   #58
orb
O-F Administrator
Ninja
 
orb's Avatar

Default

NASA / NASA JPL:
Latest Cassini Images of Enceladus on View

October 20, 2011

Raw, unprocessed images from the successful Oct. 19 flyby of Saturn's moon Enceladus by NASA's Cassini spacecraft provide new views of the moon and the icy jets that burst from its southern polar region.

Click on image for details
Raw, unprocessed image of Saturn's moon Enceladus.
Image credit: NASA/JPL/Space Science Institute


This flyby gave Cassini its first opportunity to observe Enceladus' plumes with two stars shining behind them, a dual stellar occultation.

To see the raw images, go to http://saturn.jpl.nasa.gov/photos/raw/ and click on "Search Images."

Cassini flew within about 765 miles (1,230 kilometers) of Enceladus' surface at 2:22 a.m. PDT (09:22 UTC) on Oct. 19.

{...}
orb is offline   Reply With Quote
Thanked by:
Old 10-24-2011, 07:56 PM   #59
orb
O-F Administrator
Ninja
 
orb's Avatar

Default

Universe Today: Stunning New Cassini Image: A Quartet of Moons
orb is offline   Reply With Quote
Thanked by:
Old 10-26-2011, 10:49 PM   #60
orb
O-F Administrator
Ninja
 
orb's Avatar

Default

Universe Today: Enceladus and its Water Geysers Pose Again for Cassini
orb is offline   Reply With Quote
Thanked by:
Reply

  Orbiter-Forum > Far Side of the Moon > Spaceflight News

Tags
camera, images, saturn


Thread Tools

Posting Rules
BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
Forum Jump


All times are GMT. The time now is 04:56 AM.

Quick Links Need Help?


About Us | Rules & Guidelines | TOS Policy | Privacy Policy

Orbiter-Forum is hosted at Orbithangar.com
Powered by vBulletin® Version 3.8.6
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Copyright ©2007 - 2017, Orbiter-Forum.com. All rights reserved.