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Jupiter: the "King" and His Moons
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Ganymede-V1-PIA02233-PCF-LXTT-IPF.jpgFeatures of Ganymede (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga/Lunar Explorer Italia/Italian Planetary Foundation)112 visiteThis frame was acquired by the NASA - Voyager 1 Spacecraft during its approach to Ganymede, from a distance of about 272.000 Km; the center of the picture lies at approx. 13 North Latitude and and 359 East Longitude. Ganymede (also known as Jupiter III) is the largest moon in the Solar System and the seventh moon (and third Galilean Satellite) outward from the Gas-Giant Planet Jupiter. Completing an orbit in roughly 7 (seven) Earth days, Ganymede participates in a 1:2:4 Orbital Resonance with the other Jovian moons Europa and Io, respectively. Ganymede has a diameter of about 5268 km (such as approx. 3273 miles), and, even though Ganymede is something like 8% larger than the planet Mercury, it only has about 45% of Mercury's mass; furthermore, its diameter is about 2% larger than the one of the Saturnian moon Titan, which is the second largest moon in the Solar System. Ganymede also has the highest mass of all Planetary Satellites, with approx. 2,02 times the mass of the Earth's Moon. This image shows detail on the Surface of Ganymede with a resolution of approx. 4,5 Km per pixel. What we see here, is a portion of a Region of Ganymede located in its Northern Hemisphere, near the Terminator. It shows a variety of Impact Structures, including both Rayed and Unrayed Impact Craters, as well as some odd-looking, Groove-like Surface Features (already discovered by the NASA - Voyager 1 Spacecraft in the lighter Regions of this Jovian moon). The most striking Surface Features, however, are the Bright Rayed Impact Craters which show a distinct light blueish color that, to some Observer, may also also appear white, with pink nuances, against the darker background. Ganymede's Surface is known to contain large amounts of Surface Water Ice and it appears that these (relatively) young Craters might have spread bright and (always relatively speaking) fresh Ice Materials all over the place. Likewise, the lighter color and Albedo (---> reflectivity) of the Grooved Areas suggests that over there, too, some cleaner and fresh Water Ice Material can be found. In fact, and as far as we know at the present day, Ganymede is composed of approximately equal amounts of Silicate Rock and Water Ice. It is a fully differentiated Celestial Body with an Iron-rich and still liquid core. Very recent studies suggest that, just like it has been speculated about the other Jovian moon Europa, even Ganymede may host a Subterranean Ocean, nearly 200 Km below its frozen Surface, somehow "sandwiched" between several different Layers of Rock and Ice. In addition to the above, the Surface of Ganymede is composed of two main types of Terrain: the Dark Terrain, saturated with Impact Craters and dated up to 4 (four) Billion Years ago (a Terrain that covers about a third of the moon), and the Lighter Terrain, which is crosscut by extensive Grooves and Ridges and that could be, likely, much less ancient. The cause of the Light Terrain's so-called "Disrupted Geology" is not yet fully known, but it could reasonably be the result of some powerful Tectonic Activity brought about by Tidal Heating (and let us not forget that Tidal Heating - due to Tidal Friction - may also be the primary reason why a Liquid Ocean can exist, deep down and inside the otherwise Frozen Crust of Ganymede). The NASA - Voyager 1 Spacecraft Original b/w frame has been additionally processed and then colorized, according to an informed speculation carried out by Dr Paolo C. Fienga (LXTT-IPF), in Absolute Natural Colors (such as the colors that a human eye would actually perceive if someone were onboard the NASA - Voyager 1 Spacecraft and then looked outside, towards the Jovian moon Ganymede), 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 others, the existence of different Elements present on the Surface of Ganymede, each having a different Albedo (---> Reflectivity) and Chemical Composition.MareKromium
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Ganymede-V1-PIA02233_modest.jpgGanymede in HR (Voyager 1)68 visiteThis 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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Ganymede-V1-PIA02278-PCF-LXTT-IPF.jpgFeatures of Ganymede (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga/Lunar Explorer Italia/Italian Planetary Foundation)115 visiteThis picture of Ganymede was taken by the NASA - Voyager 1 Spacecraft on the afternoon of March 5, 1979, from a range of about 253.000 Km (such as approx. 151.800 miles). The picture, that is centered at about 66 South Latitude and 3 East Longitude, shows a portion of the South Western Limb Region of Ganymede. The smallest visible Surface Features are about 2,5 Km (roughly 1,5 miles) across. The Surface of this moon shows numerous ancient Impact Craters, many of which - like we have recently seen on Planet Mercury , thanks to the NASA - Messenger Spacecraft and Orbiter - have extensive Bright Ray Systems. The light Bands that we can see crossing the whole Surface of Ganymede contain alternating bright and dark lines which, probably, represent deformation of the Icy Material that form them. Despite the NASA - Voyager 1 Spacecraft data, some evidence relevant to the existence of a tenuous Oxygen-based Atmosphere (---> a so-called "Exosphere") on Ganymede (an Exhosphere which, by the way, very similar to the one found on the other Jovian moon Europa), was discovered by the Hubble Space Telescope (HST) in the AD 1995. The HST actually observed an Airglow of Atomic Oxygen in the far-UltraViolet at the wavelengths of 130,4 and 135,6 nanometers. Such an Airglow is excited when Molecular Oxygen gets dissociated by way of Electron Impacts (and that phenomenon is a further evidence about the existence of a significant Neutral Atmosphere around Ganymede, which is predominantly composed of O2 molecules). The Oxygen, however, is not a direct evidence of the presence, on Ganymede, of some possible Earth-like Lifeforms; as a matter of fact, the Oxigen that we find in the Atmosphere of this huge moon, is thought to be produced the when Water Ice that is largely present on the Surface of Ganymede gets split into Hydrogen and Oxygen through the action of Radiation, with the Hydrogen being more rapidly lost in the circum-Ganymedian Space due to its low Atomic Mass. Furthermore, the Airglow observed over Ganymede is not spatially homogeneous like the one existing over Europa. The HST also observed two bright spots located in the Northern and Southern Hemispheres of Ganymede, near 50 of Latitude, which is exactly the Boundary Region between the Open and the Closed Field Lines of the Ganymedian Magnetosphere. These bright spots, according to our present day knowledge, could have probably been tWO Ganymedian Polar Auroras, caused by Plasma Precipitation along the Open Field Lines of its Magnetosphere. The NASA - Voyager 1 Spacecraft Original b/w frame has been additionally processed and then colorized, according to an informed speculation carried out by Dr Paolo C. Fienga (LXTT-IPF), in Absolute Natural Colors (such as the colors that a human eye would actually perceive if someone were onboard the NASA - Voyager 1 Spacecraft and then looked outside, towards the Jovian moon Ganymede), 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 others, the existence of different Elements present on the Surface of Ganymede, each having a different Albedo (---> Reflectivity) and Chemical Composition.MareKromium
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Ganymede-V1-PIA02278_modest.jpgThe limb of Ganymede (from Voyager 1)66 visiteThis 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-lor_0035286119_0x630_sci_1.jpgThe "obscure outline" of Ganymede (1)69 visiteDescription: Ganymede crossing crescent Jupiter
Time: 2007-03-04 03:50:01 UTC
Exposure: 2 msec
Target: GANYMEDE
Range: 5,9 MKMMareKromium
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Ganymede-lor_0035286134_0x630_sci_1.jpgThe "obscure outline" of Ganymede (2)65 visiteDescription: Ganymede crossing crescent Jupiter
Time: 2007-03-04 03:50:16 UTC
Exposure: 80 msec
Target: GANYMEDE
Range: 5,9 MKM MareKromium
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Ganymede_-_Juno.jpgGanymede from Juno127 visitenessun commentoMareKromium
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Himalia from 4,4MKM.jpgHimalia from 4,4 MKM82 visiteCassini 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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Himalia-lor_0035585519_0x630_sci_1-01.jpgHimalia, from New Horizons68 visiteData & 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): 14,84MareKromium
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IO - TRUE COLOR FROM GALILEO.jpgIo in true colors100 visiteNASA'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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IO 2.jpgIo & Jupiter (from Cassini)77 visiteL'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 4.jpgIo (Flying over a volcanic eruption and a sea of sulphur - Tvashtar Catena)114 visiteAn active volcanic eruption on Jupiter's moon Io was captured in this image taken on February 22, 2000 by NASA's Galileo spacecraft. Tvashtar Catena, a chain of giant volcanic calderas centered at 60 degrees north, 120 degrees west, was the location of an energetic eruption caught in action in November 1999. A dark, "L"-shaped lava flow to the left of the center in this more recent image marks the location of the November eruption. White and orange areas on the left side of the picture show newly erupted hot lava, seen in this false color image because of infrared emission. The two small bright spots are sites where molten rock is exposed to the surface at the toes of lava flows. The larger orange and yellow ribbon is a cooling lava flow that is more than more than 60 kilometers (37 miles) long. Dark, diffuse deposits surrounding the active lava flows were not there during the November 1999 flyby of Io.
This color mosaic was created by combining images taken in the near-infrared, clear, and violet filters from Galileo's camera. The range of wavelengths is slightly more than that of the human eye. The mosaic has been processed to enhance subtle color variations. The bright orange, yellow, and white areas at the left of the mosaic use images in two more infrared filters to show temperature variations, orange being the coolest and white the hottest material. This picture is about 250 kilometers (about 155 miles) across. North is toward the top and illumination from the Sun is from the west (left).
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