Saturn: the "Ringed Beauty" and His Moons |
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Enceladus in infrared26 visteCaption 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".
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The atmosphere of Enceladus23 visteCaption 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".
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Pink Rings and Enceladus, in "natural colors"21 visteCaption NASA originale:"Saturn's icy moon Enceladus hovers above Saturn's exquisite Rings in this color view from Cassini.
The Rings, made of nearly pure water ice, have also become somewhat contaminated by meteoritic dust during their history, which may span several hundred million years. Enceladus shares the Rings' nearly pure water ice composition, but appears to have eluded dust contamination through resurfacing processes that scientists are still trying to fully understand. Dust affects the Rings' color, while differences in brightness are attributable to varying particle sizes and concentrations. The images for this natural color view were taken with the Cassini spacecraft narrow-angle camera on April 5, 2005, at a distance of approximately 2,2 MKM (approx. 1,4 MMs) from Saturn through red, green and blue spectral filters. The image scale is 13 Km (about 8 miles) per pixel".
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Enceladus from 1,1 MKM26 visteCaption NASA originale:"Saturn's bright moon Enceladus hovers here, in front of the Rings darkened by Saturn's shadow.
This view is from less than 1° beneath the Ring plane. If seen from directly beneath the Rings, the planet's giant shadow would appear as an elongated half-ellipse; the acute viewing angle makes the shadow look more like a strip here. The dark shadow first takes a bite out of the rings at the right, where the distant, outermost ring material appears to taper and fade. Ring features visible in this image from the outer ring edge inward include: the A-Ring, the Cassini Division and the B-Ring. The C-Ring is the darker region that dominates the Rings here. The 2 gaps visible near the center and below the left of the center are the Titan Gap, about 77.800 Km from Saturn and an unnamed gap about 75.800 Km from the planet. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on March 7, 2005, at a distance of approx. 1,1 MKM from Enceladus, at a phase angle of 30°".
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Enceladus and Tethys21 visteCaption NASA originale:"In this unusual view, Cassini captured two icy moons of Saturn, Tethys and Enceladus, in a single narrow-angle frame. Little detail is visible on the surface of bright Enceladus, but battered Tethys shows many craters and the huge canyon system, Ithaca Chasma. Tethys has a diameter of 1.071 Km (approx. 665 miles) across, while Enceladus is 505 Km (approx. 314 miles) across.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Jan. 29, 2005, at a distance of approx. 3,7 MKM (approx. 2,3 MMs) from Tethys and 3,5 MKM (approx. 2,2 MMs) from Enceladus. Resolution in the original image was 22 Km (approx. 14 miles) per pixel on Tethys and 21 Km (approx. 13 miles) per pixel on Enceladus. The image has been contrast-enhanced and magnified by a factor of two to aid visibility".
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Enceladus: getting closer...24 visteCaption NASA originale:"This Cassini image of Saturn's moon Enceladus shows a region containing bizarre, wrinkled terrain. Enceladus is covered with bright water ice. The part of its surface visible here appears to be largely free of craters - indicating that it is geologically young (NOTA LUN-EX-IT: la mancanza di crateri non è solo indice di "gioventù geologica"; essa può anche essere dipendente dal fatto - improbabile ma da NON escludersi a-priori - che taluni processi geologici sìano ancora in corso!
Il tutto senza escludere la possibilità - anch'essa remota ma non assurda - che Encelado sia stata una "luna fortunata" e bombardata in misura inferiore rispetto alle altre...).
The first close imaging of this moon will be done by Cassini in February 2005 and should reveal many surprises. Enceladus has a diameter of 499 Km (310 miles). This view shows primarily the leading hemisphere of Enceladus and it was taken from a distance of 367.000 Km. Resolution in the original image was about 2 Km per pixel".
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Enceladus (natural colors)18 vistePrimo esperimento di elaborazione/colorizzazione Lunar Explorer Italia su Enceladus (la "Luna di Neve").
A diversa colorazione corrisponde diversa albedo; la dominante scelta è celeste, con sub-toni grigi, azzurri e bianchi.
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Crescent Enceladus, the brightest gem of Saturn's System20 visteCaption NASA originale:"In the dim light of the outer Solar System, Cassini gazed back at Saturn's brightest gem: the moon Enceladus. The icy little world presents only a slim crescent in this natural color view. Cassini has now matched the best spatial resolution on Enceladus achieved by NASA's Voyager spacecraft, and will soon have excellent coverage of the moon (at more than 10 times the resolution in this image), following a flyby planned for February 17.
When seen from its day side, Enceladus (499 Km across) has one of the brightest and whitest surfaces in the Solar System. Since it reflects most of the sunlight that strikes it, the temperature there remains at a chilly -200°C (-330° Fahrenheit).
In this view, Cassini was pointed at the leading hemisphere of Enceladus, which was in darkness at the time. The image has been rotated so that north on Enceladus is up".
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Enceladus - Diyar Planitia - from approx. 672.000 Km24 visteCaption NASA originale:"Cassini's closest look yet at bright, icy Enceladus was captured in this view, centered on the moon's trailing hemisphere. It shows some of the linear features in the terrain of the Diyar Planitia region. Enceladus is 499 Km (310 mi) across.
The image was taken in visible light with the Cassini spacecraft narrow angle camera on Dec. 14, 2004, at a distance of 672.000 Km (417.600 miles) from Enceladus and at a phase angle of 32°. The image scale is about 4 Km (2,5 miles) per pixel. The image has been magnified by a factor of two and contrast enhanced to aid visibility".
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Enceladus in visible light20 visteCaption NASA originale:"Hints of the curving linear grooves that crisscross bright, icy Enceladus are just discernible in this image captured by the Cassini spacecraft. Enceladus is almost entirely composed of water ice and has a surface as bright as snow. Its diameter is 499 Km (310 miles).
This view shows principally the leading hemisphere of Enceladus. The image was taken in visible light with the Cassini spacecraft narrow angle camera on Nov. 1, 2004, at a distance of 1,8 MKMs from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 108°. North is up. The image scale is about 11 Km (or 7 miles) per pixel. The image has been magnified by a factor of two and contrast enhanced to aid visibility of surface features".
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Enceladus20 visteCaption NASA originale:"The image shows the trailing hemisphere of Enceladus, which is the side opposite the moon's direction of motion in its orbit. Enceladus is 499 Km across.
The image was taken in visible light with the Cassini spacecraft narrow angle camera on Oct. 27, 2004, at a distance of about 766.000 Km from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 34 degrees. The image scale is 4,6 Km per pixel".
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The biggest "Geyser" in the Solar System: the Enceladus' Fountain35 visteDuring a non-targeted flyby by the Cassini spacecraft of Enceladus on Nov. 26, 2005, the Cassini's Visual and Infrared Mapping Spectrometer (VIMS) measured the spectrum of the plumes originating from the South Pole of the icy moon. The instrument captured a very clear signature of small ice particles in the plume data, at the 2,9 micron wavelength. This image of Enceladus, taken with the VIMS, shows not only the plume over the South Pole, but also the dark side of the moon, silhouetted against a foggy background of light from the E-Ring.
The bottom graph shows the measurements of the spectrum, of this background light. It shows a very similar signature of small ice particles to that in the plumes, confirming earlier expectations that Enceladus is indeed the source of the E-Ring.
Preliminary analyses suggest that the average size of the particles in the plume is about 10 microns (or 1/100.000 of a meter). The particles in the E-Ring are about 3 times smaller.
The sunlit surface of Enceladus itself, visible as a thin crescent at the bottom of the image, is also composed of water ice, but with a much larger grain size than the plume.
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