Jupiter: the "King" and His Moons

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Inizio > SOLAR SYSTEM > Jupiter: the "King" and His Moons

Ganymede-PIA00706.jpgCrescent Ganymede from Galileo53 visiteView of Ganymede from the Galileo spacecraft during its first encounter with the Jovian Satellite. North is to the top of the picture and the Sun illuminates the surface from the right. The finest details that can be discerned in this picture are about 6,7 Km across. It is 8:45:09 UT on June 26, 1996.

Ganymede-PIA00707.jpgFine details of Ganymede icy-surface53 visiteDramatic view of fine details in ice hills and valleys in an unnamed region on Jupiter's moon Ganymede. North is to the top of the picture and the sun illuminates the surface from the left. The finest details that can be discerned in this picture are only 11 mt across (similar to the size of an average house) some 2000 times better than previous images of this region. The bright areas in the left hand version are the sides of hills facing the sun; the dark areas are shadows. In the right hand version the processing has been changed to bring out details in the shadowed regions that are illuminated by the bright hillsides. The brightness of some of the hillsides is so high that the picture elements "spill over" down the columns of the picture. The image was taken on June 28, 1996 from a distance of about 1000 Km.

Ganymede-PIA00716.jpgGanymede (full disk) from about 3,4 MKM53 visiteThis color picture of Ganymede, Jupiter's largest satellite, was taken on the afternoon of March 2, 1979, by Voyager 1 from a distance of about 3,4 MKM (about 2,1 MMs). This photograph was assembled from 3 black-and-white pictures in the Image Processing Laboratory at JPL. (...)
Ganymede is slightly larger than the planet Mercury but has a density almost three times less than Mercury. Therefore, Ganymede probably consists in large part of ice. At this resolution the surface shows light and dark markings interspersed with bright spots. The large darkish area near the center of the satellite is crossed by irregular light streaks somewhat similar to rays seen on the Moon. The bright patch in the southern hemisphere is reminiscent of some of the larger rayed craters on the Moon caused by meteorite impact.

Ganymede-PIA01515.jpgThe North Pole of Ganymede (in real colors)53 visiteThis color picture as acquired by Voyager 1 during its approach to Ganymede on Monday afternoon (the 5th of March). At ranges between about 230 to 250 thousand km. The images show detail on the surface with a resolution of four and a half km. This picture is of a region in the northern hemisphere near the terminator. It shows a variety of impact structures, including both razed and unrazed craters, and the odd, groove-like structures discovered by Voyager in the lighter regions. The most striking features are the bright ray craters which have a distinctly 'bluer' color appearing white against the redder background. Ganymede's surface is known to contain large amounts of surface ice and it appears that these relatively young craters have spread bright fresh ice materials over the surface. Likewise, the lighter color and reflectivity of the grooved areas suggests that here, too, there is cleaner ice. We see ray craters with all sizes of ray patterns, ranging from extensive systems of the crater in the southern part of this picture, which has rays at least 300-500 kilometers long, down to craters which have only faint remnants of bright ejects patterns (such as several of the craters in the southern half of PIA01516; P21262). This variation suggests that, as on the Moon, there are processes which act to darken ray material, probably 'gardening' by micrometeoroid impact.

Ganymede-PIA01609.jpgRecent impact craters on Ganymede53 visiteOblique view of two fresh impact craters in bright grooved terrain near the north pole of Jupiter's moon, Ganymede. The craters postdate the grooved terrain since each is surrounded by swarms of smaller craters formed by material which was ejected out of the crater as it formed, and which subsequently reimpacted onto the surrounding surface. The crater to the north, Gula, which is 38 kilometers (km) in diameter, has a distinctive central peak, while the crater to the south, Achelous, (32 km in diameter) has an outer lobate ejecta deposit extending about a crater radius from the rim. Such images show the range of structural details of impact craters, and help in understanding the processes that form them.

North is to the top of the picture and the sun illuminates the surface from the right. The image, centered at 62 degrees latitude and 12 degrees longitude, covers an area approximately 142 by 132 kilometers. The resolution is 175 meters per picture element. The images were taken on April 5, 1997 at 6 hours, 33 minutes, 37 seconds Universal Time at a range of 17,531 kilometers by the Solid State Imaging (SSI) system on NASA's Galileo spacecraft.

Ganymede-PIA01610.jpgGanymede's surface detail: a comet fell over there?140 visiteView of a chain of craters named Enki Catena on Jupiter's moon, Ganymede. This chain of 13 craters probably formed by a comet which was pulled into pieces by Jupiter's gravity as it passed too close to the planet. Soon after this breakup, the 13 fragments crashed onto Ganymede in rapid succession. The Enki craters formed across the sharp boundary between areas of bright terrain and dark terrain, delimited by a thin trough running diagonally across the center of this image. The ejecta deposit surrounding the craters appears very bright on the bright terrain. Even though all the craters formed nearly simultaneously, it is difficult to discern any ejecta deposit on the dark terrain. This may be because the impacts excavated and mixed dark material into the ejecta and the resulting mix is not apparent against the dark background.

North is to the bottom of the picture and the sun illuminates the surface from the left. The image, centered at 39 degrees latitude and 13 degrees longitude, covers an area approximately 214 by 217 kilometers. The resolution is 545 meters per picture element. The image was taken on April 5, 1997 at 6 hours, 12 minutes, 22 seconds Universal Time at a range of 27282 kilometers by the Solid State Imaging (SSI) system on NASA's Galileo spacecraft.

Ganymede-PIA01618.jpgGanymede's surface (detail mgnf)58 visiteView 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.

Ganymede-PIA02252.jpgGanymede in HR (Voyager 1)53 visiteThis 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.

Ganymede-PIA02580.jpgCalderas on Ganymede?59 visiteThe 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.

Ganymede-PIA02582.jpgScarps on Ganymede53 visiteOriginal 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)".

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)88 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

Ganymede-V1-PIA02233_modest.jpgGanymede in HR (Voyager 1)53 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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