Jupiter: the "King" and His Moons |
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Io & Jupiter (from Cassini)47 visteL'immenso Giove ed il piccolo (ma affascinante e VIVO, geologicamente parlando) Io, in un transito immortalato dalla Sonda Cassini, in transito accanto al Signore degli Dei ed in viaggio verso il Sistema di Saturno.
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Io in true colors67 visteNASA's Galileo spacecraft acquired its highest resolution images of Jupiter's moon Io on 3 July 1999 during its closest pass to Io since orbit insertion in late 1995. This color mosaic uses the near-infrared, green and violet filters (slightly more than the visible range) of the spacecraft's camera and approximates what the human eye would see. Most of Io's surface has pastel colors, punctuated by black, brown, green, orange, and red units near the active volcanic centers. A false color version of the mosaic has been created to enhance the contrast of the color variations.
The improved resolution reveals small-scale color units which had not been recognized previously and which suggest that the lavas and sulfurous deposits are composed of complex mixtures (Cutout A of false color image). Some of the bright (whitish), high-latitude (near the top and bottom) deposits have an ethereal quality like a transparent covering of frost (Cutout B of false color image). Bright red areas were seen previously only as diffuse deposits. However, they are now seen to exist as both diffuse deposits and sharp linear features like fissures (Cutout C of false color image). Some volcanic centers have bright and colorful flows, perhaps due to flows of sulfur rather than silicate lava (Cutout D of false color image). In this region bright, white material can also be seen to emanate from linear rifts and cliffs.
Comparison of this image to previous Galileo images reveals many changes due to the ongoing volcanic activity.
Galileo will make two close passes of Io beginning in October of this year. Most of the high-resolution targets for these flybys are seen on the hemisphere shown here.
North is to the top of the picture and the sun illuminates the surface from almost directly behind the spacecraft. This illumination geometry is good for imaging color variations, but poor for imaging topographic shading. However, some topographic shading can be seen here due to the combination of relatively high resolution (1.3 kilometers or 0.8 miles per picture element) and the rugged topography over parts of Io. The image is centered at 0.3 degrees north latitude and 137.5 degrees west longitude. The resolution is 1.3 kilometers (0.8 miles) per picture element. The images were taken on 3 July 1999 at a range of about 130,000 kilometers (81,000 miles) by the Solid State Imaging (SSI) system on NASA's Galileo spacecraft during its twenty-first orbit.
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Himalia, from New Horizons12 visteData & Statistics for Himalia:
Discovered by: C. Perrine
Date of discovery: AD 1904
Mass (in Kg): approx. 9,56e+18
Mass (if Earth = 1): 1,5997e-06
Equatorial radius (in Km): approx. 93
Equatorial radius (if Earth = 1): 1,4581e-02
Mean density (in grm/cm^3): approx. 2,8
Mean distance from Jupiter (in Km): 11.480.000
Rotational period (in days): 0,4
Orbital period (in days): 250,5662
Mean orbital velocity (in Km/sec): 3,34
Orbital eccentricity: 0,1580
Orbital inclination: 27,63°
Escape velocity (in Km/sec): 0,117
Visual geometric albedo: 0,03
Magnitude (Vo): 14,84
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Himalia from 4,4 MKM50 visteCassini spacecraft captured images of Himalia, the brightest of Jupiter's outer moons, on Dec. 19, 2000, from a distance of 4,4 MKM.
This near-infrared image, with a resolution of about 27 Km (such as roughly 17 miles) per pixel, indicates that the side of Himalia facing the spacecraft is ,ore or less 160 Km (about 100 miles) in the up-down direction. Himalia probably has a non-spherical shape. Scientists believe it is a body captured into orbit around Jupiter, most likely an irregularly shaped asteroid. In the main frame, an arrow indicates Himalia. North is up. The inset shows the little moon magnified by a factor of 10, plus a graphic indicating Himalia's size and the direction of lighting (with sunlight coming from the left). Cassini's pictures of Himalia were taken during a brief period when Cassini's attitude was stabilized by thrusters instead of by a steadier reaction-wheel system. No spacecraft or telescope had previously shown any of Jupiter's outer moons as more than a "star-like" single dot.
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The "obscure outline" of Ganymede (2)13 visteDescription: Ganymede crossing crescent Jupiter
Time: 2007-03-04 03:50:16 UTC
Exposure: 80 msec
Target: GANYMEDE
Range: 5,9 MKM
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The "obscure outline" of Ganymede (1)12 visteDescription: Ganymede crossing crescent Jupiter
Time: 2007-03-04 03:50:01 UTC
Exposure: 2 msec
Target: GANYMEDE
Range: 5,9 MKM
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The limb of Ganymede (from Voyager 1)27 visteThis picture of Ganymede, Jupiter's largest satellite, was taken by Voyager 1 on the afternoon of March 5, 1979 from a range of 253.000 Km (about 151.800 miles). The picture is centered at 66° South Latitude and 3° Longitude and shows the south western limb region of Ganymede. The smallest features visible are about 2,5 Km (roughly 1,5 miles) across. The surface shows numerous impact craters, many of which have extensive bright ray systems. Light bands traversing the surface contain alternating bright and dark lines which probably represent deformation of the icy central material.
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Ganymede in HR (Voyager 1)35 visteThis picture of Ganymede was taken on the afternoon of March 5, from a range of about 272.000 Km. The center of the picture lies at 13° Lat. and 359° Long. Many bright impact craters are shown that have radial ejecta patterns. These rays lie across and therefore are younger than the bright and dark background material. Many older impact craters are shown that have lost their rays probably by impact erosion. The bright background areas contain grooves and ridges that may be caused by faulting of the surface materials.
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Scarps on Ganymede24 visteOriginal caption:"NASA's Galileo spacecraft took this image of dark terrain within Nicholson Regio, near the border with Harpagia Sulcus on Jupiter's moon Ganymede. The ancient, heavily cratered dark terrain is faulted by a series of scarps. The faulted blocks form a series of "stair-steps" like a tilted stack of books. On Earth, similar types of features form when tectonic faulting breaks the crust and the intervening blocks are pulled apart and rotate. This image supports the notion that the boundary between bright and dark terrain is created by that type of extensional faulting.
North is to the right of the picture and the Sun illuminates the surface from the west (top). The image is centered at -14° latitude and 320° longitude and covers an area approx. 16 by 15 Km (about 10 by 9 miles). The resolution is 20 mt (66 feet) per picture element. The image was taken on May 20, 2000, at a range of 2.090 Km (about 1.299 miles)".
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Calderas on Ganymede?30 visteThe shallow, scalloped depression in the center of this picture from NASA's Galileo spacecraft is a caldera-like feature 5 to 20 Km (3 to 12 miles) wide on Jupiter's largest moon, Ganymede.
Calderas are surface depressions formed by collapse above a subsurface concentration of molten material. Some shallow depressions in bright, smooth areas of Ganymede have some overall similarities to calderas on Earth and on Jupiter's moon Io. On Ganymede, caldera-like depressions may serve as sources of bright, volcanic flows of liquid water and slush - an idea supported by a Ganymede photo obtained by Galileo during its seventh orbit (PIA01614). In the more recent image here, from Galileo's 28th orbit, a tall scarp marks the western boundary of a caldera-like feature. The western scarp is aligned similarly to older tectonic grooves visible in the image, suggesting the feature has collapsed along older lines of weakness. The interior is mottled in appearance, yet smooth compared to most of Ganymede's bright terrain seen at high resolution. The eastern boundary of the caldera-like feature is cut by younger, grooved terrain. Small impact craters pepper the scene, but the lack of a raised rim argues against an impact origin for the caldera-like feature itself. Instead, water-rich icy lava may have once flowed out of it toward the east. If so, later tectonism could have erased any telltale evidence of volcanic flow fronts. Direct evidence for icy volcanism on Ganymede continues to be elusive.
North is to the top of the picture and the Sun illuminates the surface from the left. The image, centered at -24 degrees latitude and 318degrees longitude, covers an area approximately 162 by 119 kilometers(101 by 74 miles). The resolution is 43 meters (141 feet) per picture element.
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Ganymede in HR (Voyager 1)27 visteThis view of Ganymede was taken on the afternoon of March 5, 1979, from a range of about 267.000 Km (roughly 167.000 miles). A bright rayed impact crater is prominent on the left side of the frame. The ejecta material extends for a thousand kilometers. The rays are on top and therefore are younger than the brighter ridged and grooved terrain crossing the picture. These features may be breaks in the surface caused by faulting. Many older craters are visible that have lost their rays.
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Ganymede's surface (detail mgnf)48 visteView of the Marius Regio and Nippur Sulcus area of Jupiter's moon, Ganymede showing the dark and bright grooved terrain which is typical of this satellite. This regional scale view was imaged near the terminator (the line between day and night) and provides geologic context for small areas that were imaged at much higher resolution earlier in the tour of NASA's Galileo spacecraft through the Jovian system. The older, more heavily cratered dark terrain of Marius Regio is rutted with furrows, shallow troughs perhaps formed as a result of ancient giant impacts. Bright grooved terrain is younger and is formed through tectonism probably combined with icy volcanism. The lane of grooved terrain in the lower left, Byblus Sulcus, was imaged during the spacecraft's second orbit, as were Philus Sulcus and Nippur Sulcus, seen here in the upper left. Placing the small higher resolution targets of Galileo's second orbit into the context of more distant, lower resolution views of the areas surrounding and connecting them, and imaging them along Ganymede's terminator, allows for an integrated understanding of Ganymede' s geology.
North is to the top left of the picture and the sun illuminates the surface from the lower right. The image, centered at 43 degrees latitude and 194 degrees longitude, covers an area approximately 664 by 518 kilometers. The resolution is 940 meters per picture element. The image was taken on May 7, 1997 at 12 hours, 50 minutes, 11 seconds Universal Time at a range of 92,402 kilometers by the Solid State Imaging (SSI) system on NASA's Galileo spacecraft.
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