Jupiter: the "King" and His Moons
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Europa-V1-PIA00016-1-PCF-LXTT-1.jpgBizarre Image-Artifact... (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)799 visitenessun commentoMareKromium
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Europa-V2-PIA00459.jpgEuropa from Voyager 2 - the closest approach58 visiteCaption NASA originale:"This color image of the Jovian moon Europa was acquired by Voyager 2 during its close encounter on Monday morning, July 9, 1979. Europa, the size of our Moon, is thought to have a crust of ice perhaps 100 kilometers thick which overlies the silicate crust. The complex array of streaks indicate that the crust has been fractured and filled by materials from the interior. The lack of relief, any visible mountains or craters, on its bright limb is consistent with a thick ice crust hypothesis".
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Europa-crescent-V2-PIA00325.jpgCrescent Europa from Voyager 253 visiteThis mosaic of Europa, the smallest Galilean satellite, was taken by Voyager 2. This face of Europa is centered at about the 300° meridian. The bright areas are probably ice deposits, whereas the darkened areas may be the rocky surface or areas with a more patchy distribution of ice. The most unusual features are the systems of long linear structures that cross the surface in various directions. Some of these linear structures are over 1000 Km long and about 2 or 3 Km wide. They may be fractures or faults which have disrupted the surface.
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Europa-fullcolor-PIA02590_modest.jpgEuropa in full colors62 visitenessun commento
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Europa-mosaic-PIA01407.jpgDifferent surface features of Europa53 visite1. Triple bands and dark spots were the focus of some images from Galileo's eleventh orbit of Jupiter. Triple bands are multiple ridges with dark deposits along the outer margins. Some extend for thousands of kilometers across Europa's icy surface. They are cracks in the ice sheet and indicate the great stresses imposed on Europa by tides raised by Jupiter, as well as Europa's neighboring moons, Ganymede and Io. The dark spots or "lenticulae" are spots of localized disruption.
2. The Conamara Chaos region reveals icy plates which have broken up, moved, and rafted into new positions. This terrain suggests that liquid water or ductile ice was present near the surface. On Galileo's twelfth orbit of Jupiter, sections of this region with resolutions as high as 10 meters per picture element will be obtained.
3. Mannann'an Crater is a feature newly discovered by Galileo in June 1996. Color and high resolution images (to 40 meters per picture element) from Galileo's fourteenth orbit of Jupiter will offer a close look at the crater and help characterize how impacts affect the icy surface of this moon.
4. Cilix, a large mound about 1.5 kilometers high, is the center of Europa's coordinate system. Its concave top and what may be flow like features to the southwest of the mound are especially intriguing. The origin of this feature is unknown at present. Color, stereo, and high resolution images (to 65 meters per picture element) from Galileo's fifteenth orbit of Jupiter will offer new insights and resolve questions about its origin.
5. Images of Agenor Linea (white arrow) and Thrace Macula (black arrow) with resolutions as high as 30 meters per picture element will be obtained during Galileo's sixteenth orbit of Jupiter. Agenor is an unusually bright lineament on Europa. Is the brightness due to new ice, and if so, does it represent recent activity? Could the dark region of Thrace Macula be a flow from ice volcanism?
6. Images of Europa's south polar terrain obtained during Galileo's seventeenth orbit of Jupiter will offer insights into the processes which are active in this region. Is the ice crust thicker near Europa's poles than near the equator? The prominent dark line running from upper left to lower right through the center of this image is Astypalaea Linea. It is a fault about the length of the San Andreas fault in California and is the largest such fault known on Europa. Images with resolutions of 48 meters per picture element will be obtained to examine its geologic structure.
7. This long lineament, Rhadamanthys Linea. is spotted with dark "freckles". Are these freckle features formed by icy volcanism? Is this an early form of a triple band? Stereo and high resolution (to 46 meters per picture element) obtained during Galileo's eighteenth orbit of Jupiter may indicate whether the lineament is the result of volcanic processes or is formed by other surface processes.
8. During Galileo's nineteenth orbit of Jupiter, images of Europa will be taken with very low sun illuminations, similar to taking a picture at sunset or sunrise. The object will be to search for backlit plumes issuing from icy volcanic vents. Such plumes would be direct evidence of a liquid ocean beneath the ice. Resolutions will be as high as 40 meters per picture element. This picture was simulated image from Galileo data obtained during the spacecraft's second orbit of Jupiter in September 1996.
North is to the top of the pictures. During orbit 13, the Galileo spacecraft was behind the sun from our vantage point on Earth so it did not obtain or transmit data from that orbit. The left two images in the bottom row were obtained by NASA's Voyager 2 spacecraft in 1979; the remaining images were obtained by the Solid State Imaging (SSI) system on NASA's Galileo spacecraft in 1996.
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Europa.jpg"Faces & Phases" of Europa53 visitenessun commentoMareKromium
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Europa_and_Jupiter.jpgI am speechless...164 visiteC'è un luogo del Sistema Solare dove pensiamo di trovare forme di vita extraterrestri. Ha un nome molto familiare ed è uno dei satelliti di Giove: si chiama Europa. Questo mondo ha delle caratteristiche geologiche che lo rendono estremamente interessante da decenni. Fuori è coperto da una spessa crosta ghiacciata, ma dentro contiene un enorme oceano, proprio come quelli che abbiamo qui sulla Terra (vedi Nota 1).
La sua caratteristica unica suggerisce che l'acqua oceanica può "in qualche modo muoversi attraverso il guscio e raggiungere la superficie", ha affermato Alyssa Rhoden, scienziato del Southwest Research Institute in Colorado. Se l'affermazione è, in effetti, vera, "i nutrienti e l'energia possono circolare tra l'oceano, il guscio di ghiaccio e la superficie, e questo può essere benefico per la vita".
L'imminente Europa Clipper della NASA è una missione rivoluzionaria per capire di più sul corpo planetario e sul suo potenziale di abitabilità. Verrà lanciato nel 2024 e arriverà nel 2030.
Rhoden ha dichiarato: "Ho iniziato a fare ricerche su Europa 22 anni fa e ho sempre avuto le stesse immagini con cui lavorare,
"Quindi, direi che sono ESTREMAMENTE eccitato per i nuovi set di dati che saranno forniti da Clipper. Per quanto riguarda l'abitabilità, probabilmente ci sono molti modi in cui informerà l'abitabilità, ma quello che sono più interessato a vedere è la prova dell'acqua liquida all'interno il guscio di ghiaccio".
Alla domanda su quale vita si possa trovare su Europa, Rhoden ha scherzato: "Le balene spaziali, ovviamente" (vedi Nota 2).
Nota 1: roba vecchia di oltre 28 anni;
Nota 2: se questa tizia è una "scienziata", allora è davvero la fine...MareKromium
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Ganymede and Europa-PIA02574.jpgGanymede and Europa: so different and yet so similar!53 visiteThis frame compares a HR view of Arbela Sulcus on Ganymede (top) with the gray band Thynia Linea on another Jovian moon, Europa (bottom), shown to the same scale. Both images are from NASA's Galileo spacecraft.
Arbela Sulcus is one of the smoothest lanes of bright terrain identified on Ganymede, but subtle striations are apparent here along its length. This section of Arbela contrasts markedly from highly fractured terrain to its west and dark terrain to its east.
On Europa, gray bands such as Thynia Linea have formed by tectonic crustal spreading and renewal. Such bands have sliced through and completely separated pre-existing features in the surrounding bright, ridged plains. The younger prominent double ridge Delphi Flexus cuts across Thynia Linea. The scarcity of craters on Europa attests to the relative youth of its surface compared to Ganymede's.
Unusual for Ganymede, it is possible that Arbela Sulcus has formed by complete separation of Ganymede's icy crust, like bands on Europa. Tests of this idea come from detailed comparisons of their internal shapes and the relationships to the surrounding structures.
In the Ganymede image, north is to the top of the picture and the Sun illuminates the surface from the west. The image, centered at -15degrees latitude and 347 degrees longitude, covers an area approximately 34 by 26 kilometers (21 by 16 miles). The resolution is 34 meters (112 feet) per picture element. The image was taken on May 20, 2000, at a range of 3,370 kilometers (2,094 miles).
In the Europa image, north is to the upper-right of the picture and the Sun illuminates the surface from the northwest. The image, centered at-66 degrees latitude and 161 degrees longitude, covers an area approximately 44 by 46 kilometers (27 by 29 miles). The resolution is 45 meters (147 feet) per picture element. The image was taken on September 26, 1998, at a range of 3,817 kilometers (2,371 miles).
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Ganymede-P-51236218280_1b20779992_o.pngGanymede94 visitenessun commentoMareKromium
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Ganymede-PIA00353~0.jpgGanymede from 2,6 MKM53 visiteThis picture was taken on March 4, 1979 at 2:30 A.M. PST by Voyager 1 from a distance of about 2,6 MKM (such as about 1,6 MMs). Ganymede is Jupiter's largest satellite with a radius of about 2600 Km which means about 1,5 times that of our Moon. Ganymede has a bulk density of only approximately 2,0 g/cc (almost half that of the Moon).
In the light of the above, Ganymede is probably composed of a mixture of rock and ice. The features here, the large dark regions, in the northeast quadrant, and the white spots, resemble features found on the Moon, mare and impact craters respectively. The long white filaments resemble rays associated with impacts on the lunar surface. The various colors of different regions probably represent differing surface materials. There are several dots on the picture of single color (blue, green, and orange) which are the result of markings on the camera used for pointing determinations and are not physical markings.
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Ganymede-PIA00380_modest.jpgGanymede from 250.000 Km53 visiteCaption NASA originale:"This picture of Ganymede, Jupiter's largest satellite, was taken by Voyager 1 on the afternoon of March 5, 1979, from a range of about 250,000 km. The center of the picture is at 60 north latitude and 318 longitude and the distance across the bottom of the photograph is about 1000 km. The smallest features visible in this picture are about 5 km across. This picture shows impact craters many of which display ray systems probably consisting largely of icy material thrown out by the impacts. Peculiar systems of sinuous ridges and grooves traverse the surface and are best seen near the terminator".
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Ganymede-PIA00496.jpgFrost on crater-tops of Ganymede53 visiteScientists believe that water-ice frosts are the likely cause for the brightening seen around the circular rims of these craters located at a high northern latitude (57°) on Jupiter's moon Ganymede in this image taken by NASA's Galileo spacecraft on September 6, 1996. The image shows the same kind of bright, high-latitude surface areas as those first seen by the Voyager 1 spacecraft in 1979, but at higher resolution (this image spans about 18 Km - or 11 miles on a side). Even though the Sun is shining from the south, the north-facing walls of the ridges and craters are brighter than the walls facing the Sun. This is interpreted to mean that the very bright north-facing slopes are covered with surface water-ice frosts, and that these frosts preferentially accumulate in such high-latitude locations.
Galileo scientists say that at the HR seen in Galileo images, the high-latitude brightness seen by Voyager 1 might be partly attributable to frosts forming on cooler, north-facing slopes. The right-hand side of the image is dominated by a north-south line of impact craters; the smallest ones at the top are about 2 kilometers (1.2 miles) in diameter and the large one at the bottom is about 5 kilometers (about 3 miles) in diameter. Ganymede is the largest moon in the solar system, larger than the planet Mercury and nearly the size of Mars.
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