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Saturn: the "Ringed Beauty" and His Moons
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Pandora-PIA11499.jpgPandora53 visiteCaption NASA:"The thin shadow of the moon Pandora cuts across Saturn's narrow F-Ring.
As Saturn approaches its August 2009 Equinox, the planet's moons cast shadows onto the Rings. Pandora (about 81 Km, or approx. 50 miles across) is on the left of the image. Other bright points of light in the image are background stars.
This view looks toward the unilluminated side of the Rings from about 55° above the Ring-Plane. The image was taken in Visible Light with the Cassini Spacecraft narrow-angle camera on April 16, 2009. The view was obtained at a distance of approx. 1,3 MKM (such as about 808.000 miles) from Saturn and at a Sun-Saturn-Spacecraft, or Phase, Angle of 98°.
Image scale is roughly 8 Km (about 5 miles) per pixel".MareKromium
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Pandora-PIA12690.jpgPandora54 visiteCaption NASA:"The Cassini Spacecraft captured this close view of Saturn's moon Pandora during the Fly-By on June, 3, 2010.
Pandora is approx. 81 Km (a little mora than 50 miles) across and orbits beyond Saturn's thin F-Ring, which is shepherded by Pandora and Prometheus.
This view looks toward the Saturn-facing side Pandora. North on Pandora is up and rotated 20° to the left.
The image was taken in Visible Light with the Cassini Spacecraft narrow-angle camera. The view was obtained at a distance of approx. 101.000 Km (about 63.000 miles) from Pandora and at a Sun-Pandora-Spacecraft, or Phase, Angle of 28°.
Image scale is 603 meters (1980 feet) per pixel".MareKromium
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Pandora.pngPandora: nice and close (Credits: Dr Marco Faccin and Elisabetta Bonora)136 visiteUnbelievable view.MareKromium
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PandoraandDione-PIA07625.jpgPandora and Dione53 visiteOriginal caption:"This view looks up toward the sunlit side of Saturn's rings, as Dione and Pandora trundle by. The moons are on the near side of the Rings and the Planet's shadow stretches across the Rings in the background.
The Cassini spacecraft took this image in visible light with its narrow-angle camera on Sept. 16, 2005, at a distance of approx. 2,4 MKM (such as roughly 1,5 MMs) from Saturn. The image scale is of about 12 Km (7 miles) per pixel on Dione".
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Phoebe (3D).jpgThree-dimensional Phoebe53 visiteCaption NASA originale:"The Sun is coming from the left, illuminating craters and bumps on the surface, along with a prominent ridge-like feature in the middle. Bright material, likely to be ice, is exposed atop this ridge-like feature as well as around small craters and down the slopes of large craters. There are also bright streaks on steep slopes, perhaps where loose material slid downhill during the seismic shaking of impact events".
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Phoebe-1-PIA06117.jpgPhoebe: names, features and details53 visiteCaption NASA originale:"The craters are named for the Argonauts, explorers of Greek mythology who sought the 'Golden Fleece' (--->Vello d'Oro). Argo was the name of their ship. The largest crater, approximately 100 Km (62 miles) across, is named after the leading Argonaut, Jason. Phoebe is an outer moon of Saturn and is 220 Km (136 miles) across.
The image montage displays mosaics made of individual, very HR images: from 80 meters (260 feet) to 200 meters (660 feet) per pixel".
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Phoebe-2-PIA06117.jpgPhoebe: names, features and details53 visitevedi il commento al frame che precede
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Phoebe-PIA06064-PCF-LXTT-IPF-1.jpgPhoebe (Absolute Natural Colors - Credits for the additional process. and color.: Dr Paolo C. Fienga/Lunar Explorer Italia/Italian Planetary Foundation)72 visitePhoebe's possibole true nature is partly revealed in this image-mosaic of two frames taken during the NASA - CASSINI Spacecraft's Fly-By that occurred on June 11, 2004. The image shows evidence for the emerging view that Phoebe may be an ice-rich Celestial Body coated with a thin Layer of Dark Material (probably Dust). This phenomenon has been observed on other Icy Satellites, such as Ganymede, in the Jovian System: when an impactor slammed into the Surface of Phoebe, the collision excavated fresh, bright Material - probably Water Ice - underlying the Surface Layer of Dust and other rocky debris. A further evidence supporting this hypothesis can be seen on some Crater Walls where the darker Material appears to have slid downwards, so to expose more light-colored Material. However, some areas of the image that are particularly bright - especially near the lower right - are just over-exposed. Small bright Impact Craters visible in the picture are probably fairly young Surface Features.
In addition to that, a number of interesting circumstances seem to indicate that Phoebe may have originated in the Outer Solar System. In fact, Phoebe's highly irregular and Dark Surface, its retrograde orbit, the presence, on its Surface, of a huge variety of large and small Impact Craters and, last but not least, its extremely low Average Density, appear consistent with the hypothesis that Phoebe was once part of the Kuiper Belt, before being captured by Saturn's Gravity (which is, most likely, the same origin of quite a few Minor moons of the Gas-Giant Planets Uranus, Neptune, Saturn and Jupiter).
This spectacular view was obtained at a Phase, or Sun-Phoebe-Spacecraft, Angle of 84°, and from a distance of approximately 32.500 Km (such as aabout 20.200 miles). The image scale is approximately 190 meters (624 feet) per pixel.
These image-mosaic (which is made of two Original NASA - CASSINI Spacecraft b/w frames published on the NASA - Planetary Photojournal with the ID n. PIA 06064) have been additionally processed and then colorized, according to an informed speculation carried out by Dr Paolo C. Fienga (LXXT/IPF), in Absolute Natural Colors (such as the colors that a human eye would actually perceive if someone were onboard the NASA - CASSINI Spacecraft and then looked outside, towards the Saturnian Outer moon, Phoebe), by using an original technique created - and, in time, dramatically improved - by the Lunar Explorer Italia Team. Different colors, as well as different shades of the same color, mean, among other things, the existence of different Elements (Minerals) present on the Surface of Phoebe, each having a different Albedo (---> Reflectivity) and Chemical Composition.MareKromium
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Phoebe-PIA06065.gifRevolving Phoebe (a GIF-Movie by NASA/JPL/Space Science Institute)126 visiteCaption NASA:"Phoebe rotates through nearly one full rotation in this GIF sequence of 9 frames, taken on Cassini's approach to the small Celestial Body on June, 10, 2004. Phoebe rotates on its axis once every 9 hours and 16 minutes; this sequence spans 8 hours and 14 minutes; all 360° of Longitude on Phoebe are visible in the sequence.
The Surface is clearly covered by impact craters of a wide range of sizes, up to 40% of the diameter of the moon, creating rugged topography, illustrated dramatically along the Terminator and Limb.
The images that make up this sequence were obtained at a Sun-Phoebe-Spacecraft angle of 87° and from distances ranging from 877.453 Km (544.898 miles) to 688.924 Km (427,822 miles). The image scale in this sequence ranges from 5,3 to 4,1 Km per pixel. To aid visibility, the images were magnified three times via linear interpolation; no contrast enhancement was performed".MareKromium
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Phoebe-PIA06066.jpgPhoebe133 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
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Phoebe-PIA06070.jpgThe "true shape" of Phoebe53 visiteCaption NASA originale:"This colorful graphic illustrates that despite Phoebe's bumpy, irregular topography, the moon has a fairly round shape. A digitally rendered shape model of Phoebe was constructed using Cassini imaging data obtained before and after the spacecraft's close flyby of the Saturnian moon on June 11, 2004.
The average diameter of Phoebe is about 214 Km. The four views of the model are each separated by a 90° rotation; the upper left is centered at 0° West longitude. The others show regions of the moon centered at 90, 180 and 270° West longitude, as labeled. The coloring of the models corresponds to the height of Phoebe's surface, relative to the lowest point - a range of about 16 Km - going from blue (low) to red (high). Interestingly, much of this range in height occurs in 1 large crater, visible in the 180° West view".
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Phoebe-PIA06075.jpgPhoebe's SkyLine55 visiteImages like this one, showing bright wispy streaks thought to be ice revealed by subsidence of crater walls, are leading to the view that Phoebe is an ice-rich body overlain with a thin layer of dark material. Obvious down slope motion of material occurring along the walls of the major craters in this image is the cause for the bright streaks, which are over-exposed here. Significant slumping has occurred along the crater wall at top left.
The slumping of material might have occurred by a small projectile punching into the steep slope of the wall of a pre-existing larger crater. Another possibility is that the material collapsed when triggered by another impact elsewhere on Phoebe. Note that the bright, exposed areas of ice are not very uniform along the wall. Small craters are exposing bright material on the hummocky floor of the larger crater.
Elsewhere on this image, there are local areas of outcropping along the larger crater wall where denser, more resistant material is located. Whether these outcrops are large blocks being exhumed by landslides or actual 'bedrock' is not currently understood.
The crater on the left, with most of the bright streamers, is about 45 kilometers (28 miles) in diameter, front to back as viewed. The larger depression in which the crater sits is on the order of 100 kilometers (62 miles) across. The slopes from the rim down to the hummocky floor are approximately 20 kilometers (12 miles) long; many of the bright streamers on the crater wall are on the order of 10 kilometers (6 miles) long. A future project for Cassini image scientists will be to work out the chronology of slumping events in this scene.
This image was obtained at a phase, or Sun-Phoebe-spacecraft, angle of 78 degrees, and from a distance of 11,918 kilometers (7,407 miles). The image scale is approximately 70 meters (230 feet) per pixel. No enhancement was performed on this image.
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