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| Piú votate - Saturn: the "Ringed Beauty" and His Moons |
Saturn_and_Moons-N00173684_-83-82-MF-LXTT.jpgTrue Planets (Absolute Natural Colors; credits for the additional process. and color.: Dr Marco Faccin - Lunexit Team)179 visitenessun commentoMareKromium
(3 voti)
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Saturnian_Lightnings-00.jpgSaturnian Storm and Lightnings (CTX Frame - credits: NASA/JPL/SSI)137 visiteA powerful lightning storm brewing in Saturn's atmosphere since January has become the solar system's longest continuously observed thunderstorm, astronomers have announced.
The storm breaks the record duration of 7,5 months set by another thunderstorm observed on Saturn by NASA's Cassini Spacecraft between November 2007 and July 2008. The current thunderstorm on Saturn is the ninth that has been measured since Cassini swung into orbit around Saturn in July 2004.
Lightning discharges in Saturn's Atmosphere emit very powerful radio waves, which are measured by the antennas and receivers of the Cassini Radio and Plasma Wave Science (RPWS) instrument. The radio waves are about 10.000 times stronger than their terrestrial counterparts and originate from huge thunderstorms in Saturn's Atmosphere with diameters of about 1900 miles (3057,746 Km).
The observations of this latest thunderstorm will be presented by Georg Fischer of the Austrian Academy of Sciences at the European Planetary Science Congress in Potsdam, Germany, on Sept. 15. "These lightning storms are not only astonishing for their power and longevity, the radio waves that they emit are also useful for studying Saturn's Ionosphere, the charged layer that surrounds the planet a few thousand kilometers above the cloud tops," Fischer said. "The radio waves have to cross the Ionosphere to get to Cassini and thereby act as a natural tool to probe the structure of the layer and the levels of ionization in different regions."
Results from Cassini's RPWS instrument have confirmed previous studies of the Voyager spacecraft indicating that levels of ionization are approx. 100 times higher on the day-side than the night side of Saturn's Ionosphere.
Lightning storms on Saturn usually occur in a region that nicknamed "Storm Alley" by scientists. The region lies 35° South of Saturn's Equator.
"The reason why we see lightning in this peculiar location is not completely clear," Fischer said. "It could be that this latitude is one of the few places in Saturn's Atmosphere that allow large-scale vertical convection of water clouds, which is necessary for thunderstorms to develop. However, it may be a seasonal effect. Voyager observed lightning storms near the Equator, so now that Saturn has passed its Equinox on Aug. 11, we may see the storms move back to Equatorial Latitudes."
The lightning's presence was confirmed in another way: During Cassini's last close flyby of Titan on Aug. 25, Cassini's view of Saturn was obscured by Titan for a half-hour, and no lightning was observed. "Although we know from Cassini images where Saturn lightning comes from, this unique event was another nice proof for their origin," Fischer also said.MareKromium
(3 voti)
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Saturnian_Lightnings-01.jpgSaturnian Storm and Lightnings (EDM - credits: NASA/JPL/SSI)136 visiteA monster storm spawning bolts of lightning 10.000 times more powerful than any seen on Earth is raging on the Ringed Planet Saturn.
The powerful electrical storm cropped up in Saturn's Southern Hemisphere five months ago, when it was first spotted by NASA's Cassini Spacecraft, and has persevered to become the Planet's longest continuously recorded tempest to date.
"We saw similar storms in 2004 and 2006 that each lasted for nearly a month, but this storm is longer-lived by far, said Georg Fischer, an associate with Cassini's radio and plasma wave science team at the University of Iowa, Iowa City, in a statement. And it appeared after nearly two years during which we did not detect any electrical storm activity from Saturn."
Cassini's radio and plasma wave science instrument first picked up signals from the storm's lightning bursts on Nov. 27, 2007, with the probe's cameras catching their first visual glimpse on Dec. 6. Images of the storm show it as a smudge on Saturn's otherwise creamy cloud bands.
"The electrostatic radio outbursts have waxed and waned in intensity for five months now," Fischer said.
Electrical storms on Saturn are similar to thunderstorms on Earth, but much larger. They can span thousands of miles and generate radio bursts from lightning that can be thousands of times more powerful than Earthly lightning bolts, said mission scientists, who named a massive lightning storm in 2004 "Dragon".
The current electrical tempest is mired in a region of Saturn that mission scientists have dubbed "Storm Alley" because of its frequent and intense storms. Every few seconds the storm belches intense radio pulses consistent with lightning that can be detected even when the weather itself is over the horizon and out of direct view from Cassini.
Researchers hope that by tracking the Saturnian weather, they may gain new insights into the processes behind the Planet's lightning, as well as how it changes as the seasons shift from Summer to Autumn in Saturn's Southern Hemisphere.
In order to see the storm, the imaging cameras have to be looking at the right place at the right time, and whenever our cameras see the storm, the radio outbursts are there," said Ulyana Dyudina, a Cassini imaging team associate at the California Institute of Technology in Pasadena, Calif.
Cassini's onboard instruments have tracked the storm every 10 hours and 40 minutes, when Saturn's rotation brings it into view, though amateur astronomers are also watching over the tempest from Earth.
"Since Cassini's camera cannot track the storm every day, the amateur data are invaluable," said Fischer. "I am in continuous contact with astronomers from around the world."
Launched in 1997, Cassini arrived at Saturn in 2004 and has spotted a series of odd storms while studying the Ringed Planet and its many moons. The probe has captured views of a hurricane-like storm near the South Pole of Saturn and recorded a massive lightning storm about 2175 miles wide (3500,3145 Km) wide in 2006.MareKromium
(3 voti)
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Saturnian_Lightnings-02.jpgSaturnian Storm and Lightnings (EDM - credits: NASA/JPL/SSI)166 visiteScientists are tracking the strongest lighting storm ever detected at Saturn. The storm is larger than the continental United States, with electrical activity about 1000 times stronger than the lightning on Earth. Radio outbursts were first detected by NASA's Cassini Spacecraft on Jan. 23. The storm is about 2175 miles wide (approx. 3500 Km). "It's really the only large storm on the whole planet," said Andrew Ingersoll, a member of the Cassini imaging team.
Earth-based amateur astronomers were able view Saturn's dayside with their telescopes when Cassini could not. The amateurs' images of Saturn provided the first visual confirmation of the storm.
The storm is in a Region of the Southern Hemisphere referred to as "Storm Alley" by scientists because of the high level of storm activity observed there. The latitude of the new storm matches that of the "Dragon Storm", which was a powerful emitter of radio noise and was imaged by Cassini in 2004. It may be a reemergence of that storm or a new storm, scientists said.
Sunlight reflected from Saturn's Rings (called "Ringshine") provided illumination needed to allowing the storm and other cloud features to be seen in a new Cassini image.MareKromium
(3 voti)
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Saturnian_Lightnings-03.jpgSaturnian Lightnings155 visiteNASA's Cassini Spacecraft captured images of lightning at Saturn that allowed scientists to create the first movie showing lightning flashing on another Planet.
"The Visible Light images tell us a lot about the lightning," said Ulyana Dyudina, a Cassini imaging team associate based at the California Institute of Technology (Caltech) in Pasadena, Calif., who was the first to see the flashes. "Now we can begin to measure how powerful these storms are, where they form in the cloud layer and how the optical intensity relates to the total energy of the thunderstorms."
After waiting years for Saturn to dim enough for the Spacecraft's cameras to be able to detect bursts of light, scientists were able to create the movie, complete with an accompanying soundtrack that features the crackle of radio waves emitted when lightning bolts struck.
"This is the first time we have the visible lightning flash together with the radio data," said Georg Fischer, a radio and plasma wave science team associate based at the Space Research Institute in Graz, Austria. "Now that the radio and visible light data line up, we know for sure we are seeing powerful lightning storms."
Cassini, launched in 1997, and NASA's Voyager mission, launched in 1977, had previously captured radio emissions from storms on Saturn.
A belt around the gas giant, where Cassini previously detected radio emissions and bright, conservative clouds, even earned the nickname "storm alley." Cassini's cameras, however, had been unable to obtain pictures of lightning flashing.
Since the Robotic Spacecraft's arrival at Saturn in 2004, it has been difficult for Cassini to see lightning because the planet is very bright and reflective. Sunlight that shines off of Saturn's enormous Rings makes even the night side of Saturn brighter than a full-moon night on Earth.
The Equinox period around August 2009 finally brought enough darkness needed for Cassini's cameras. During Equinox, the Sun shone directly over the Planet's Equator, lighting the Rings edge-on only, leaving the bulk of the Rings in shadow.
The movie and radio data collected by the scientists suggest extremely powerful storms, with lightning that flashes as brightly as the brightest super-bolts of lightning on Earth, according to Andrew Ingersoll, a Cassini imaging science subsystem team member at Caltech.
"What's interesting is that the storms are as powerful or even more powerful at Saturn as on Earth," Ingersoll said. "But they occur much less frequently, with usually only one happening on the planet at any given time, though it can last for months."
The first images of lightning on Saturn were captured in August 2009, during a storm that lasted from January to October 2009, longer than any other observed lightning storm in the Solar System.
In order to make a video, scientists needed more pictures with brighter lightning and strong radio signals. Data collected during a shorter subsequent storm, which occurred from November through mid-December 2009, was also used.
The frames in the video were obtained over a period of 16 minutes on Nov. 30, 2009. The flashes lasted less than one second. The images also show a cloud as long as 1900 miles (3057,746 Km) across, with the regions illuminated by the lightning flashes reaching approx. 190 miles (305,7746 Km) in diameter. Scientists used the width of the lightning flashes to gauge the depth of the bolts below the cloud tops.
Lightning that strikes on Earth and Saturn emit radio waves at a frequency that can cause static on an AM radio. The audio in the video approximate that static sound, based on Saturn's electrostatic discharge signals that were detected by Cassini's radio and plasma wave science instrument.
Scientists monitoring the Cassini Orbiter were busy during this Equinox period, having already observed clumps in Saturn's Rings that are as high as the Rocky Mountains.
The Cassini-Huygens mission is a joint project involving NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of Caltech, manages the Cassini-Huygens mission for NASA's Science Mission Directorate in Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at the Jet Propulsion Laboratory.MareKromium
(3 voti)
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Phoebe-PIA06066.jpgPhoebe136 visiteCaption NASA:"Early images returned from the first detailed reconnaissance of Saturn's small outer moon, Phoebe, show breathtaking details in the moon's pockmarked Surface that already have imaging scientists puzzling over the body's history. The images are only a preview of what to expect from the High Resolution images which will show details about 10 times smaller.
Phoebe has revealed itself to be a rugged, heavily cratered body, with overlapping craters of varying sizes.
This morphology suggests an old Surface. There are apparently many craters smaller than 1 km, indicating that projectiles probably smaller than 100 meters once pummeled Phoebe.
Whether these objects were Cometary or Asteroidal in origin, or were the debris that resulted from impacts on other bodies within the Saturn System, is hotly debated. There is also variation in surface brightness across the body.
In the first image (at left) in which Phoebe looks somewhat like a sideways skull, the large crater near the bottom displays a complex and rugged interior. The lower right hand part of Phoebe appears to be covered by bright wispy material.
The second, Higher Resolution image further reveals the moon's battered Surface, including a crater near the right hand edge with bright rays that extend outward from its center. This suggests that dark material coats the outside. Features reminiscent of those seen on the Martian moon Phobos -- such as Linear Grooves -- are faintly visible in the upper part of this image.
There are suggestions of Linear Ridges or Grooves and of Chains of Craters, perhaps radial to a large crater just hidden on the un-illuminated region in the upper left.
Left to right, the two views were obtained at phase, or Sun-Phoebe-Spacecraft, Angles of approximately 86°, and from distances ranging from 143.068 Km (88.845,228 miles) to 77,441 kilometers (48.090,861 miles); for reference, Cassini's closest approach to Phoebe was approximately 2068 Km (1284,228 miles). The image scale ranges from 0,86 to 0,46 Km per pixel. No enhancement of any kind has been performed on the images".MareKromium
(3 voti)
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Rhea-PIA12809-PCF-LXTT.jpgThe Heavily Fractured Surface of Rhea (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)106 visiteCaption NASA:"Icy Fractures on Saturn's moon Rhea reflect Sunlight brightly in this High-Resolution Mosaic created from images captured by NASA's Cassini Spacecraft during its March 2, 2010, Fly-By. This Fly-By was the closest one of Rhea up to then.
This mosaic of six images shows the Westernmost portion of the moon's "Wispy" Terrain. Among the interesting features depicted here is a very straight East-West Fracture near the top center of the mosaic that intersects two North-South Fractures. The large Crater at the bottom left of the mosaic is Inmar Crater (about 55 Km, or approx. 34 miles across).
The closest approach of the Spacecraft to Rhea during this encounter was of about 100 Km (approx. 62 miles). These images were obtained approximately 30 minutes later, at an altitude of about 16.000 Km (roughly 10.000 miles).
This mosaic shows part of the side of Rhea that always faces Saturn. The images were re-projected in an orthographic projection centered on Terrain at 7° North Latitude and 296° West Longitude. The mosaic itself shows Features centered on Terrain that is at 6° North Latitude and 293° West Longitude.
The images were taken with the Cassini Spacecraft narrow-angle camera. The view was obtained at a Sun-Rhea-Spacecraft, or Phase, Angle of about 2°. So, Cassini was almost directly between Rhea and the Sun as it acquired these images.
Image scale is roughly 85 meters (280 feet) per pixel".MareKromium
(3 voti)
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Tethys-PIA12802.jpgThe "Face" of Tethys (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)82 visiteCaption NASA:"Geologic faults among craters on Saturn's moon Tethys are depicted in this image captured during a Fly-By of the moon by NASA's Cassini Spacecraft on Aug. 14, 2010.
The brightly illuminated, prominent Impact Crater near the bottom middle of this image has been dissected by numerous parallel Faults that run diagonally across the image. The presence of the Faults that cut through the Crater and the movement of Surface Materials have made the Crater outline somewhat non-circular.
Near the center of the image, running diagonally from the left to right, is an old Graben, such as a "Linear Depression of the Terrain between two Faults".
Below these Faults and near the middle top of the image is a large ancient Impact Crater that is so highly overprinted by more recent Craters that it can barely be recognized.
On the left of the image, there are some horizontal lines that can be seen very faintly cutting across Craters. These lines are artifacts of missing data in the raw image that could not be eliminated through processing the image.
This view looks toward the Leading Hemisphere of Tethys. The view is centered on terrain at 59° North Latitude and 79° West Longitude.
The image was taken in Visible Light with the Cassini Spacecraft narrow-angle camera. The view was acquired at a distance of approx. 40.000 Km (such as about 25.000 miles) from Tethys and at a Phase Angle of 103°. Image scale is roughly 234 meters (767 feet) per pixel".MareKromium
(3 voti)
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Hyperion-MF-PCF-LXTT-2.jpgHyperion and its Surfacing Hydrocarbons (Absolute Natural Colors; credits for the additional process. and color.: Drr Marco Faccin and Paolo C. Fienga)74 visiteNota: questa colorizzazione "Naturale Assoluta" (e cioè che risponde a quello che, a nostro parere, un essere umano vedrebbe se si trovasse a bordo della Sonda CASSINI) è un prodotto UNICO ed ESCLUSIVO del "Lunexit Team". MareKromium
(3 voti)
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Hyperion-MF-PCF-LXTT-4.jpgHyperion and its Surfacing Hydrocarbons (Absolute Natural Colors; credits for the additional process. and color.: Elisabetta Bonora and Paolo C. Fienga)68 visiteNota: questa colorizzazione "Naturale Assoluta" (e cioè che risponde a quello che, a nostro parere, un essere umano vedrebbe se si trovasse a bordo della Sonda CASSINI) è un prodotto UNICO ed ESCLUSIVO del "Lunexit Team". MareKromium
(3 voti)
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Hyperion-MF-PCF-LXTT-5.jpgHyperion and its Surfacing Hydrocarbons (Absolute Natural Colors; credits for the additional process. and color.: Elisabetta Bonora and Paolo C. Fienga)68 visiteNota: questa colorizzazione "Naturale Assoluta" (e cioè che risponde a quello che, a nostro parere, un essere umano vedrebbe se si trovasse a bordo della Sonda CASSINI) è un prodotto UNICO ed ESCLUSIVO del "Lunexit Team". MareKromium
(3 voti)
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Rhea-EB-LXTT.jpgCratered Terminator (Absolute Natural Colors; credits for the additional process. and color.: Elisabetta Bonora and Paolo C. Fienga - Lunexit Team)60 visitenessun commentoMareKromium
(3 voti)
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