Saturn: the "Ringed Beauty" and His Moons

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Inizio > SOLAR SYSTEM > Saturn: the "Ringed Beauty" and His Moons

Ultimi arrivi - Saturn: the "Ringed Beauty" and His Moons

Tethys from Voyager2.jpgTethys, from Voyager 260 visiteCaption NASA originale:"Voyager 2 obtained this view of Saturn's moon Tethys on Aug.25 from a distance of 540.000 Km. It shows the numerous impact craters and fault valleys of a very ancient surface. Tethys itself is 1.090 km. (approx. 675 mi) in diameter and the great chasm seen at the top of this image extends about 1.700 Km (approx. 1.050 mi) halfway across the satellite. The largest impact crater visible here is 90 Km (approx. 55 mi) in diameter".Mar 20, 2005

Tethys in natural colors-V2.jpgTethys in natural colors59 visiteCaption NASA originale:"Voyager 2 obtained this image of Tethys on Aug. 25, when the spacecraft was 594.000 Km from this moon of Saturn. This photograph was compiled from images taken through the violet, clear and green filters of Voyager's narrow-angle camera. Tethys shows two distinct types of terrain - bright, densely cratered regions and relatively dark, lightly cratered planes that extend in a broad belt across the satellite. The densely cratered terrain is believed to be part of the ancient crust of the satellite; the lightly cratered planes are thought to have been formed later by internal processes. Also clearly seen is a trough that runs parallel to the terminator (the day-night boundary, seen at right). This trough is an extension of the huge canyon system that also Voyager 1 saw and photographed . This system extends nearly 2/3rds the distance around Tethys".Mar 20, 2005

Telesto.jpgTelesto60 visiteCaption NASA originale:"Saturn's moon Telesto is visible below and to the left of center in this image from the Cassini spacecraft.
Telesto (only 24 Km across) shares the orbit of Saturn's moon Tethys (1.071 Km across), leading the larger moon in its path by 60°. Similarly sized Calypso (22 Km across) trails Tethys by the same amount. These positions, called Lagrange points, are dynamically stable. In being co-orbital moons of Tethys, Telesto and Calypso are like the Trojan moons of Jupiter, which occupy Lagrange points and orbit 60° ahead and behind of Jupiter. The Saturnian moon Dione also has companion moons: Helene, which leads Dione in its orbit and the Cassini-discovered trailing Lagrange moon, Polydeuces. This image was taken in visible light with the Cassini spacecraft narrow angle camera on Jan. 18, 2005, at a distance of approximately 3,7 MKM from Telesto. Resolution in the image is 7 Km per pixel. Telesto has been brightened by a factor of two to aid visibility". Mar 20, 2005

Hyperion-PIA06608[1].jpgThumbling Hyperion101 visiteCaption NASA originale:"As it loops around Saturn, Cassini periodically gets a good view of Saturn's moon Hyperion. Hyperion chaotically tumbles around in its orbit and is perhaps the largest irregularly-shaped moon in the Solar System. New details about this oddball worldlet will certainly come to light in September, 2005, when Cassini is slated to approach Hyperion at a distance of 990 Km. The images were taken in visible light with the Cassini spacecraft narrow-angle camera in October 2004 and February 2005, at distances ranging from 1,3 to 1,6 MKM (such as from approx. 808.000 to 994.000 MMs) from Hyperion and at phase angles ranging from 42 to 66°. Resolution in the original images was 8 to 10 Km (approx. 5 to 6 miles) per pixel.
The images have been contrast-enhanced and magnified by a factor of two to aid visibility".Mar 19, 2005

Dione&Titan-PIA06607.jpgDione and Titan61 visiteCaption NASA originale:"As artful as it is informative, this captivating portrait captures Saturn's wispy moon Dione over the shoulder of smoggy Titan in a single inspiring scene. Dione is 1.118 Km (approx. 695 miles) across and Titan is 5.150 Km (such as approx. 3.200 miles) across.
The image was taken in visible green light with the Cassini spacecraft narrow-angle camera on Feb. 18, 2005, at a distance of approximately 1,3 MKM (808.000 miles) from Dione and 2,1 MKM (1,3 MMs) from Titan. The image scale is 8 Km (5 miles) per pixel on Dione and 13 Km (8 miles) per pixel on Titan".Mar 18, 2005

Dione-N00030564.jpgA "hat-trick" of Moons!56 visiteAncora un'immagine spettacolare che ci mostra, questa volta, addirittura una "tripletta" di lune Saturniane. Le caratteristiche superficiali ci aiutano a riconoscerne almeno due, cioè quelle più grandi ed - apparentemente - più vicine (diremmo che si tratti di Dione e Rhea). Sapreste individuare la terza?Mar 17, 2005

Enceladus-PIA07370.jpgThe atmosphere of Enceladus58 visiteCaption NASA originale:"The graphic shows the magnetic field observed by Cassini along its trajectory plotted in a vector form. Even though the spacecraft altitude was almost 500 Km (310 miles) at closest approach and the flyby was upstream of the moon (where the interaction is expected to be weaker) Cassini's magnetometer observed bending of the magnetic field consistent with its draping around a conducting object, which indicates that the Saturnian plasma is being diverted away from an extended atmosphere".Mar 17, 2005

Enceladus-PIA07459.jpgEnceladus in infrared63 visiteCaption NASA originale:"This infrared color image of Enceladus was obtained by the Cassini visual infrared mapping spectrometer on March 9, 2005, when the Cassini spacecraft was 9.145 Km away from Enceladus.
Enceladus shows substantial differences in composition or, more likely, particle size on its surface. Redder areas correspond to larger grain sizes, and appear to be correlated with craters and ridged regions. The surface of Enceladus is nearly pure water ice; no other components have been identified yet. The middle of the image is located at the equator near a longitude of 210°.
The image is about 100 Km square and it shows the ratio of reflected light at 1,34 and 1,52 microns, wavelengths that are not visible to the human eye".Mar 17, 2005

Enceladus-PIA06210.jpgEnceladus' "crispy & fractured" surface (false colors)58 visiteTo human eyes, Enceladus appears almost completely white, but false color reveals intriguing details. This view is a composite of images taken using filters sensitive to ultraviolet (centered at 338 nnmts), green (centered at 568 nnmts), and near-infrared (centered at 930 nnmts) light and has been processed to accentuate subtle color differences. The uppermost surface of these terrains appears uniformly grey in this picture, suggesting that they are covered with materials of homogeneous composition and grain size. However, the walls of many of the fractures appear to be somewhat bluer than typical surface materials. It is possible that the difference in color identifies outcrops of solid ice on the walls of fractures, or ice with different grain-sizes, compared to powdery surface materials. It is also possible that the color identifies some compositional difference between buried ice and ice at the surface. The surface is peppered with craters of all sizes, from the 21-Km diameter crater at the top of the image, down to tiny craters near the limit of resolution. The prominent crater at the top contains a central, domelike structure more than 11 kilometers (7 miles) in diameter. The dome, the crater -- and indeed the entire scene -- is sliced by a complex network of fractures ranging in width from hundreds of meters in some places, to over three kilometers (2 miles) in others.Mar 17, 2005

Enceladus-PIA06209.jpgEnceladus' "crispy & fractured" surface (false colors)58 visiteExtending through the center of this image is a system of rifts 3 Km wide and lanes of grooved terrain 20 Km wide, which separate 2 distinct geological provinces. To the right of the boundary is older, cratered terrain - a region peppered with craters ranging from 10 Km in diameter, down to craters near the limit of resolution. The region is believed to be old because it has accumulated a relatively high density of impact craters over time and the topography is soft and muted, suggesting that it is covered by a layer of particulate materials. The cratered terrain is cut crosswise by numerous faults and fractures ranging in width from hundreds of meters to a few Km. On the left side of the scene are grooved, icy plains. This broad, relatively flat region is scored by an extensive band of parallel grooves that appear to subdivide the surface into narrow lanes approx. 1 Km wide. The low abundance of impact craters and crisp relief on topographic features here imply that this region is geologically much younger than the cratered terrain at the right.Mar 17, 2005

Enceladus-PIA06208.jpgEnceladus (full-disk) - false colors58 visiteCaption NASA originale:"During its very close flyby on March 9, 2005, the Cassini spacecraft captured this false-color view of Saturn's moon Enceladus, which shows the wide variety of this icy moon's geology. Some geological regions on Enceladus are old and retain large numbers of impact craters; younger areas exhibit many generations of tectonic troughs and ridges. Subtle differences in color may indicate different ice properties, such as grain sizes, that will help unravel the sequence of geologic events leading to the current strange landscape. In the early 1980's, NASA's Voyager mission to the outer planets revealed a strikingly similar arrangement of terrains on Miranda, an icy moon of Uranus (see PIA 00141). Miranda is 470-Km-wide (290 miles), nearly as large as Enceladus (504 Km). The similarities in size and tectonic history on these objects may suggest that remarkably similar physical processes have controlled the separate geological evolutions of these bodies. The Sun illuminates Enceladus from the left, leaving part of it in shadow and blocking out part of the view of Saturn. This view shows the anti-Saturn hemisphere, centered nearly on the equator". Mar 17, 2005

Enceladus-PIA06207.jpgEnceladus' "crispy & fractured" surface56 visite(...) The rims and interiors of many craters seem to be sliced by a pervasive system of narrow, parallel grooves into slabs or lanes that typically are about 1 Km in width. The widely varied appearances of fractures in this region attest to the fact that the surface of Enceladus has been shaped by a long history of intense tectonic activity. The oldest fractures are characterized by a soft, muted appearance and are overprinted by numerous, superimposed impact craters. More recent fractures exhibit topographic relief that is relatively "crisp" in appearance, and they appear to slice through pre-existing impact craters and older fractures. On the right side of the image is a conspicuous and twisted network of ridges and troughs forming a distinct tectonic region on Enceladus. The paucity of craters and the sharp appearance of the topography in this area indicate that this is a relatively young terrain on Enceladus. One possibility is that the walls of the fractures expose outcrops of solid ice, or ice with different grain-sizes compared to powdery surface materials that blanket flat-lying surfaces. It is also possible that the color identifies some compositional difference between buried ice and ice at the surface. The distinct coloration of "youthful" fracture walls are nearly absent in the oldest fractures. This is consistent with the possibility that the older fractures are covered with a drape of particulate material which mantles nearly all the oldest features on the satellite.Mar 17, 2005

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