Category: Saturn

Saturn crescent with Mimas, Rhea and Tethys. Image credit: NASA/JPL/SSI. Click to enlarge
This view of Saturn shows a thick crescent of the planet bathed in sunlight with the rest in shadow. Three moons are visible in this photograph: Mimas, Ryea and Tethys. Cassini took this photograph on March 11, 2006 when it was approximately 2.8 million kilometers (1.8 million miles) from Saturn.

The tilted crescent of Saturn displays lacy cloud bands here along with a bright equatorial region and threadlike ring shadows on the northern hemisphere.

Three moons are visible here. Mimas (397 kilometers, or 247 miles across) at left and faint, is aligned with the ringplane. At right are Rhea (1,528 kilometers, or 949 miles across, at top) and Tethys (1,071 kilometers, or 665 miles across, below Rhea).

The image was taken in polarized infrared light with the Cassini spacecraft wide-angle camera on March 11, 2006, at a distance of approximately 2.8 million kilometers (1.8 million miles) from Saturn. The image scale is 166 kilometers (103 miles) per pixel.

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

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

The Dragon storm. Image credit: NASA/JPL/SSI Click to enlarge
On Earth we have hurricane season, and a welcome break in between. On Saturn, it’s always hurricane season. Hurricanes here on Earth are caused by warm ocean temperatures heated by the Sun that feed energy and water up into the storm clouds. On Saturn, the energy comes from the internal heat of the planet, which is still slowly shrinking after its formation billions of years ago.

On Saturn, it may be a very long wait for the calm after a storm. As big and destructive as hurricanes on Earth can be, at least they don’t last long. Not like those on Saturn, where storms may rage for months or years. Viewed from space, hurricanes on Earth and the huge atmospheric disturbances observed on Saturn look similar. But their differences are greater and offer intriguing insights into the inner workings of the ringed world being investigated by scientists on NASA’s Cassini mission.

Earth’s hurricanes and Saturn’s storms each have swirling clouds, convection, rain and strong rotating winds. “Hurricanes on Earth are low pressure centers at the ground and high pressures at the top where the storms flatten out,” says Dr. Andrew Ingersoll, member of the Cassini imaging team and professor of planetary science at the California Institute of Technology in Pasadena, Calif. “Storms on Saturn could be like hurricanes if what we’re seeing is the top of the clouds.”

The frequency of storms on Saturn seems to be about the same as on Earth, and the fraction of planet occupied by storms is also similar. Not surprisingly, since Saturn is so much larger than Earth — nine Earths would fit across its equator — its storms are bigger. Hurricane Katrina stretched more than 380 kilometers (240 miles) across, for example, while two storms the Cassini spacecraft spotted in February 2002 each extend more than 1,000 kilometers (620 miles) in diameter, about the size of Texas or France.

On Earth, hurricane winds can exceed 240 kilometers per hour (150 miles per hour), similar to the speed of the jet stream, just about the fastest wind on the planet. Though spinning furiously, hurricanes travel along at a much slower pace — eight to 32 kilometers per hour (five to 20 miles per hour). Saturn is different because its jet stream is much stronger. “Saturn’s a very windy place,” says Ingersoll. “The jet stream on Saturn blows ten times faster than on Earth, up to a thousand miles per hour.” Saturn’s winds are like conveyor belts between which storms appear to roll like ball bearings, he explains. “While we don’t know the wind speeds within the storms, a good guess is that they are slower than the winds in the jet stream.”

What most distinguish storms on Saturn from those on Earth are the forces that drive them and physical differences between the two planets.

The heat that drives hurricanes on Earth comes from the oceans, vast reservoirs of solar energy. The oceans are also the source of moisture for convection, which draws energy from the ocean into the atmosphere and creates storm clouds and driving rainfall. Hurricanes quickly fade once they make landfall, once the plug is pulled on their power source.

The fuel for Saturn’s storms is quite different. The interior of the planet acts like an ocean and stores energy, but the energy does not come from the sun. “Saturn makes it own heat, which it got when the pieces that made the planet crashed together during the violent history of the early solar system,” says Ingersoll.

Saturn’s atmosphere has all the ingredients necessary for hurricane-like storms including heat and water vapor, he continues, so there’s no need for that first step in hurricane development where the ocean evaporates. And, without a solid surface like Earth’s ocean, Saturn’s storms behave very differently.

“You’d think that when two storms merge, for example, that you’d get a bigger storm,” says Ingersoll, “but they seem to stay the same size. They can also split apart. They may go on forever, merging and splitting.”

Scientists will be able to study Saturn’s storms more closely next year, when the Cassini spacecraft tours a region in the southern hemisphere mission scientists that call storm alley.

With the exception of a few storms, like the dramatic Dragon Storm observed by the Cassini spacecraft last year, most of Saturn’s storms are unnamed, unlike those on Earth. That may change, says Ingersoll, when scientists get to know them better.

Original Source: NASA News Release

Titan and small Epimetheus behind Saturn’s rings. Image credit: NASA/JPL/SSI. Click to enlarge
This Cassini photograph shows Saturn’s large, smoggy moon Titan partly obscured by the planet’s rings. Another of Saturn’s moons, tiny Epimetheus, is visible as a dot just to the left of Titan. Cassini took this photograph on March 9, 2006 when it was approximately 4.1 million kilometers (2.5 million miles) from Titan.

This poetic scene shows the giant, smog-enshrouded moon Titan behind Saturn’s nearly edge-on rings. Much smaller Epimetheus (116 kilometers, or 72 miles across) is just visible to the left of Titan (5,150 kilometers, or 3,200 miles across).

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on March 9, 2006, at a distance of approximately 4.1 million kilometers (2.5 million miles) from Titan. The image scale is 25 kilometers (16 miles) per pixel on Titan. The brightness of Epimetheus was enhanced for visibility.

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

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

Dynamic Saturn. Image credit: NASA/JPL/SSI. Click to enlarge
Saturn, up close and personal. In this Cassini image, you can see the subtle, swirling storms that roll across Saturn’s atmosphere. Unlike the Earth, Saturn is still a planet in formation; it’s continuing to slowly contract, which generates the massive amounts of heat that drive its dramatic weather systems. Cassini took this photograph on March 7, 2006 when it was 2.9 million kilometers (1.8 million miles) from Saturn.

Streamers, swirls and vortices roll across the dynamic face of Saturn.

Unlike Earth, where most of the weather is driven by the Sun, Saturn’s storms and circulation are driven in part by internal heating. Amazingly, the planet is still contracting (ever so slightly) from its formation, more than 4.5 billion years ago. This gravitational contraction liberates energy in the form of heat.

The image was taken in polarized infrared light with the Cassini spacecraft narrow-angle camera on March 7, 2006, at a distance of approximately 2.9 million kilometers (1.8 million miles) from Saturn. The image scale is 17 kilometers (10 miles) per pixel.

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

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

Prometheus acting on Saturn’s F ring. Image credit: NASA/JPL/SSI. Click to enlarge
One of the most amazing images sent back by the Cassini spacecraft shows one of Saturn’s shepherd moons, Prometheus, tugging a stream of particles away from the F ring. Scientists from Queen Mary, University of London have developed a model that explains the forces at work in this dramatic interaction. It was originally believed that Prometheus steals ring particles, but it now appears that it just borrows them as it comes past, and they drift back into the ring system after the moon sweeps by.

Images from Saturn’s F ring region obtained by the Cassini Imaging Science Subsystem (ISS) cameras have revealed structure never seen before in a planetary ring.

The rings around all the giant planets in our Solar System are thought to be stabilised by small ‘shepherd moons’ that orbit in or near the rings and stabilize them by gravitational influences.

The narrow F ring of Saturn ? which lies just outside the spectacular main rings – is tended by two small shepherds. Prometheus (100 km in diameter) orbits just inside the F ring, while Pandora (85 km in diameter) moves around Saturn just outside the F ring.

Periodic structures such as azimuthal gaps ? ‘channels’ of low optical depth – and ‘streamers’ have been discovered. These features can be seen in Movie1. The origin of these features has been explored by a team at Queen Mary, University of London (QMUL) using numerical integrations.

On Tuesday 4 April, Carlos Chavez of QMUL will be explaining to the RAS National Astronomy Meeting in Leicester the results of their computer models, which explain the close and complex relationship between Prometheus and the tangled F ring.

“The models are in excellent agreement with structures observed in the Cassini images,” said Chavez.

“We have found that the gaps are not due to a lack of particles, but to a forced change in orbital elements by a close encounter with Prometheus,” he explained. “The moon’s gravity temporarily pulls some of the particles away from the main stream as it passes by.”

“It is like a crowd of people walking in a number of lines in the same direction down a street. Suddenly, someone else comes from the other side of the street and collides with a few of them. He then tells them to come with him, and walks away. Only people in the closest lines follow him, which produces gaps in the crowd. However, they return back to the main group shortly afterwards.”

The most dramatic case will happen in late 2009, when the F ring and Prometheus are anti-aligned. Once per orbit during this anti-alignment Prometheus will be at apoapsis (its furthest point from Saturn) and the nearby ring particles will be at periapsis (closest point to Saturn). At that time, Prometheus and the ring particles are at their closest to each other.

The QMUL team explored how these events will affect collisions between the ring particles and Prometheus. They found a low number of collisions – only 0.6% of the particles collided per orbit. This was unexpected, since it was originally thought that Prometheus is a ‘thieving moon’, stealing particles from the F ring. What actually happens is that the particles are only temporarily pulled away and then drift back into the ring.

The ring-moon interactions are also likely to have an effect on the surface of Prometheus. Like our Moon and most other planetary satellites, Prometheus has a synchronous rotation, always showing the same face to Saturn.

The team at QMUL investigated the location on Prometheus’ surface where the particles would be expected to collide. They found that, in the synchronous co-rotating reference frame, the collisions surprisingly occurred on the trailing face of Prometheus, and preferably in the equatorial region.

This scenario has important implications for the surface features of Prometheus, and the team expects to find differences in albedo (reflectivity) between the trailing and leading faces.

“It would be like a man colliding with other people while facing continuously in a particular direction and hitting them with only one side of his body,” said Chavez.

Other members of the QMUL team examining the links between Prometheus and the F ring are: Prof. Carl D. Murray, Dr. Kevin Beurle, Dr. Nicholas J. Cooper, and Dr. Michael W. Evans.

Original Soure: RAS News Release

Giant Saturn and its moon Tethys. Image credit: NASA/JPL/SSI. Click to enlarge
This Cassini photograph shows half of Saturn shrouded in shadow, with its moon Tethys hanging in the foreground. A gigantic storm that was first sighted in January 2006 continues to rage in Saturn’s southern hemisphere. This image was taken on February 18, 2006, when Cassini was 2.8 million kilometers (1.7 million miles) from Saturn.

The Cassini spacecraft looks toward giant Saturn and its moon Tethys, while a large and powerful storm rages in the planet’s southern hemisphere. The storm was observed by the Cassini spacecraft beginning in late Jan. 2006, and was at the time large and bright enough to be seen using modest-sized telescopes on Earth.

The fact that the storm stands out against the subtle banding of Saturn at visible wavelengths suggests that the storm’s cloud tops are relatively high in the atmosphere.

Tethys is 1,071 kilometers (665 miles) across.

The image was taken in visible light with the Cassini spacecraft wide-angle camera on Feb. 18, 2006, at a distance of approximately 2.8 million kilometers (1.7 million miles) from Saturn. The image scale is 162 kilometers (101 miles) per pixel on Saturn.

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

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

Small moonlets resides within Saturn’s rings. Image credit: NASA/JPL/SSI Click to enlarge
A whole new class of mini-moons have been discovered lurking inside Saturn’s rings. These tiny moons are about 100 metres (300 feet) across, and there could be as many as 10 million in total in the ring system. Scientists have wondered for many years if Saturn’s rings are the result of a larger object that was shredded by Saturn gravity millions of years ago, and these moonlets could help provide the answer. They would be remnants of the former object, and could give insights into what its structure was.

Scientists with NASA’s Cassini mission have found evidence that a new class of small moonlets resides within Saturn’s rings. There may be as many as 10 million of these objects within one of Saturn’s rings alone.

The moonlets’ existence could help answer the question of whether Saturn’s rings were formed through the break-up of a larger body or are the remnants of the disk of material from which Saturn and its moons formed.

“These moonlets are likely to be chunks of the ancient body whose break-up produced Saturn’s glorious rings,” said Joseph Burns of Cornell University, Ithaca, N.Y., a co-author of the report.

Careful analysis of high-resolution images taken by Cassini’s cameras revealed four faint, propeller-shaped double streaks. These features were found in an otherwise bland part of the mid-A Ring, a bright section in Saturn’s main rings. Cassini imaging scientists reporting in this week’s edition of the journal Nature believe the “propellers” provide the first direct observation of how moonlets of this size affect nearby particles. Cassini took the images as it slipped into Saturn orbit on July 1, 2004.

Previous measurements, including those made by NASA’s Voyager spacecraft in the early 1980s, have shown that Saturn’s rings contain mostly small water-ice particles ranging from less than 1 centimeter (one-half inch) across to the size of a small house. Scientists knew about two larger embedded ring moons such as 30-kilometer-wide (19-mile) Pan and 7-kilometer-wide (4-mile) Daphnis. The latest findings mark the first evidence of objects of about 100 meters (300 feet) in diameter. From the number of moonlets spotted in the very small fraction of the A ring seen in the images, scientists estimated the total number of moonlets to be about 10 million.

“The discovery of these intermediate-sized bodies tells us that Pan and Daphnis are probably just the largest members of the ring population, rather than interlopers from somewhere else,” said Matthew Tiscareno, an imaging team research associate at Cornell and lead author on the Nature paper.

Moons as large as Pan and Daphnis clear large gaps in the ring particles as they orbit Saturn. In contrast, smaller moonlets are not strong enough to clear out the ring, resulting in a partial gap centered on the moonlet and shaped like an airplane propeller. Such features created by moonlets were predicted by computer models, which give scientists confidence in their latest findings.

“We acquired this spectacular, one-of-a-kind set of images immediately after getting into orbit for the express purpose of seeing fine details in the rings that we had not seen previously,” said Carolyn Porco, Cassini imaging team leader and co-author. “This will open up a new dimension in our exploration of Saturn’s rings and moons, their origin and evolution.”

The detection of moonlets embedded in a ring of smaller particles may provide an opportunity to observe the processes by which planets form in disks of material around young stars, including our own early solar system. “The structures we observe with Cassini are strikingly similar to those seen in many numerical models of the early stages of planetary formation, even though the scales are dramatically different,” said co-author Carl Murray, an imaging team member at Queen Mary, University of London. “Cassini is giving us a unique insight into the origin of planets.”

For images showing the propeller-shaped features, visit: http://www.nasa.gov/cassini , http://saturn.jpl.nasa.gov and http://ciclops.org .

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 Cassini-Huygens mission for NASA?bfs Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

Original Source: NASA/JPL/SSI News Release

Spoke features in Saturn’s B-ring captured by Voyager 2 in August 1981. Image credit: NASA Click to enlarge
When Voyager first visited Saturn 26 years ago, it returned photographs of unusual spokelike structures in the rings. The Hubble Space Telescope confirmed the spokes in the 1990s, but then they faded out. It’s believed that the spokes are caused when electrically charged particles collect above the surface of the rings, scattering light from the Sun differently than the rings themselves. Scientists think they might be due to return around July this year, as they depend on the ring’s angle towards the Sun, which is now decreasing.

Unusual spokes that appear fleetingly on the rings of Saturn only to disappear for years at a time may become visible again by July, according to a new study spearheaded by the University of Colorado at Boulder.

The spokes, which are up to 6,000 miles long and 1,500 miles in width, were first spotted 26 years ago by the Voyager spacecraft, said CU-Boulder Professor Mihaly Horanyi of the Laboratory for Atmospheric and Space Physics. But when the Cassini spacecraft arrived at Saturn in July of 2004, the striking radial features that cut across Saturn’s ring plane were nowhere to be found — an event that disappointed and puzzled many scientists, he said.

The Hubble Space Telescope occasionally observed the ring spokes in the late 1990s, said Horanyi, a professor of physics at CU-Boulder. But the spokes gradually faded, a result of Saturn’s seasonal, orbital motion and its tilted axis of rotation that altered the light-scattering geometry.

“The spokes were switched off by the time Cassini arrived,” said Horanyi. “We think it is a seasonal phenomena related to the sun rising and setting over the ring plane that changes the physical environment there, making it either friendly or hostile to their formation.”

A paper on the subject appears in the March 17 issue of Science magazine. The paper was authored by doctoral student Colin Mitchell and Horanyi of CU-Boulder’s LASP, Ove Havnes of the University of Trosmo in Norway and Carolyn Porco of the Space Science Institute in Boulder.

The spokes are made up of tiny dust particles less than a micron in width — about 1/50th the width of a human hair — that collect electrostatic charges in the plasma environment of the rings and become subject to electrical and magnetic forces, said Horanyi. The right conditions cause them to gain an extra electron, allowing them to leap en masse from the surface of ring debris for brief periods, collectively forming the giant spokes that appear dark against the lit side of the rings and bright against the unlit side of the rings.

The researchers hypothesize that the conditions for the spokes to form are correlated to a decrease in the angle of the ring plane to the sun. “Because the rings are more open to the sun now than when Voyager flew by, the charging environment above the rings has prevented the formation of the spokes until very recently,” the researchers wrote in Science.

Cassini first imaged a “puny version” of Saturn’s spoke rings from a distance of 98,000 miles in early September that were only about 2,200 miles in length and about 60 miles wide, said Horanyi. The team believes the spoke sighting may have been an “early bird” event.

As the ring plane angle decreases when Saturn is near its two seasonal equinoxes, the conditions appear to become more suitable for the formation of the eerie spokes, said Horanyi. Although Cassini currently is orbiting too close to the ring plane to make observations, the researchers expect the spoke activity to have returned by the time the spacecraft increases its inclination in July 2006.

Once the spokes are visible again, the research team believes there will be spoke activity for about eight years, based on the fact that it takes Saturn about 30 Earth-years to complete one orbit around the sun, said Horanyi. The eight-year period should be followed by about six-to-seven years of a spoke hiatus, he said.

The dust grains levitated by plasma during spoke-forming periods are probably hovering less than 50 miles above the rings themselves and they scatter light from the sun differently than do the rings themselves, he said.

But there are still many questions about the spokes, said Horanyi. “We don’t know if they form by rapidly expanding, or if they form all at once,” he said. During the Voyager mission, they were absent during one observation, but fully developed in a follow-up observation made just five minutes later, Horanyi said.

“This is a weird phenomena; we don’t have the full story on it yet,” he said.

Original Source: CU-Boulder News Release

Titan’s multiple hazy layers. Image credit: NASA/JPL/SSI Click to enlarge
This is a composite photograph consisting of 24 photos taken by Cassini of Saturn’s moon Titan. Up at the top of Titan it’s possible to see several layers of clouds in the atmosphere. The top layer is at an altitude of 500 km (300 miles) and probably consists of water ice. Why the atmosphere is separate like this is still a mystery, but scientists think it might have something to do with waves in the atmosphere.

This composite of 24 images from the Cassini spacecraft shows multiple layers in Titan’s stratospheric haze. The most prominent layer is located about 500 kilometers (300 miles) above the surface and is seen at all latitudes, encircling the moon. The material in this layer is probably a condensed substance, possibly water ice.

Several other layers are most apparent in the north polar hood (at top), but this view also shows some at other latitudes. The mechanisms that produce these layers are not understood, but waves in the atmosphere are thought to play a significant role.

The images in this composite were taken over a period of 23 minutes. The images were processed to enhance fine detail and then were combined to create this view. North on Titan (5,150 kilometers, or 3,200 miles across) is up.

The images were taken in visible light with the narrow-angle camera on Jan. 27, 2006 at a distance of approximately 2.3 million kilometers (1.4 million miles) from Titan and at a Sun-Titan-spacecraft, or phase, angle of 155 degrees. Image scale is 13 kilometers (8 miles) per pixel.

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

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

Saturn’s moon Enceladus. Image credit: NASA/JPL/SSI Click to enlarge
Now that Cassini has uncovered how Enceladus is spewing out water ice from geysers at its southern pole, scientists have an explanation for Saturn’s E ring. This is Saturn’s outermost ring, which consists of a diffuse cloud of particles stretching from Mimas to Titan. Cassini’s magnetometer matched the signature of the ice geysers to the particles in the E-ring, linking one to the together.

Saturn’s moon Enceladus is the source of Saturn’s E-ring, confirms research published today.

Writing in the journal Science, scientists show how a plume of icy water vapour bursting out of the South Pole of Enceladus replenishes the water particles that make up the E-ring and creates a dynamic water-based atmosphere around the small moon. The E-ring is Saturn’s outermost ring and is composed of microscopic particles. It is very diffuse and stretches between the orbit of two of Saturn’s moons, Mimas and Titan.

Scientists discovered the dynamic atmosphere during three separate fly-bys of Enceladus by the Cassini spacecraft in February, March and July 2005. Cassini Huygens is a joint NASA/ESA mission to study the Saturnian system.

The team working on results from the magnetometer instrument were surprised to discover what they believed was an atmosphere on their first fly-by, 1176km from the moon’s surface. After a second flyby at 500km confirmed their observations, they persuaded the Cassini Project to take the next flyby much closer to Enceladus in order to investigate further.

On this flyby, at 175km, measurements from all the different instruments on the spacecraft confirmed the presence of an atmosphere. Later remote sensing observations of the moon revealed a plume of water vapour coming from the moon’s South Pole.

The atmosphere was also seen to change between the flybys, with a particularly extended atmosphere observed during the first one and a more concentrated atmosphere seen during subsequent flybys. The team believe that changing levels of activity by the plume at the South Pole were causing these changes in the atmosphere.

Professor Michele Dougherty, from Imperial College London’s Department of Space and Atmospheric Physics, Principal Investigator on Cassini’s magnetometer instrument and lead author of one of the papers, said: “When we observed signatures of an atmosphere on the first distant flyby we were very surprised because it was so unexpected to observe such signatures so far away from the moon.

“It was extremely exciting to have all the other instruments confirm our initial discovery, particularly when it was found that the atmosphere was changing from flyby to flyby and was closely linked with the subsequent plume observations at the South Pole. In addition this discovery clearly shows the importance of having a multi-instrument spacecraft such as Cassini since it enables us to combine a whole range of different data sets thereby allowing us to gain a much better overall understanding of complex physical systems.

Measurements of the temperature of Enceladus showed that, surprisingly, there is a concentration of heat around the South Pole, with the hottest point located over one of the fractures in the planet’s surface. The scientists believe that this heat signature shows internal processes within Enceladus causing the icy plume, by heating the moon’s ice.

Original Source: PPARC News Release