Jupiter: the "King" and His Moons |
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As Time Goes By...On Io!20 visteVolcanoes on Jupiter's moon Io are compared in these images from Galileo spacecraft (right) taken in early September of 1997 and from the Voyager spacecraft (left) taken in 1979. Prometheus (bright ring in upper right) was first seen as an erupting volcano by the Voyager spacecraft and still features an active plume. A smaller active plume was discovered at the volcano Culann Patera (dark feature at lower left) by the Galileo spacecraft. Prometheus has displayed similar characteristics such as size, shape and brightness to Galileo's cameras as it did to Voyager's. However, several intriguing differences are also apparent. There appears to be a new dark lava flow emanating from the vent of Prometheus, and the plume is now erupting from a position about 75 Km (about 46,5 miles) west from where the hot spot resided in 1979. It is not known if the plume source is the same or if the plume is now emanating from a new source. Overall, scientists studying Galileo images of Io see that a wide variety of surface changes have occurred on Io since 1979. The Galileo image was taken at a range of about 487,000 kilometers (about 302,000 miles) from Io. The Voyager image was taken from about 800,000 kilometers (about 500,000 miles).
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Io: five views of the one and the same25 visteFive color views of Jupiter's moon Io, as seen by NASA's Galileo spacecraft camera, were taken between the 25th and the 29th of June, 1996 Universal Time. The color is a composite of the red, green, and violet filters of the on board imaging system with the brightness of the violet bandpass increased to provide better color discrimination. The full disk images were intended for color mapping of Io's surface and for comparison to Voyager images. Where images overlap several features can be seen to change in relative brightness, perhaps due to unusual light scattering behavior or active phenomena. The crescent images were intended primarily for color imaging of active volcanic plumes on the bright limb and these images showed that the Voyager-era Loki plumes were no longer active and revealed a new plume at Ra Patera. The smallest features which can be discerned in the 5 views range from 9 to 23 kilometers and provide our best look at Io since the 1979 Voyager flybys. Sub-spacecraft longitudes on Io (from upper left to lower right) are 69, 338, 264, 211, and 221 W. North is to the top.
Launched in October 1989, Galileo entered orbit around Jupiter on December 7, 1995. The spacecraft's mission is to conduct detailed studies of the giant planet, its largest moons and the Jovian magnetic environment.
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Io: three views of the one and the same26 visteThree views of the full disk of Jupiter's volcanic moon, Io, each shown in natural and enhanced color. These three views, taken by Galileo in late June 1996, show about 75 percent of Io's surface. North is up. The top disks are intended to show the satellite in natural color (but colors will vary with display devices) while the bottom disks show enhanced color (near-infrared-, green-, and violet-filtered images) to highlight details of the surface. These images reveal that some areas on Io are truly red, whereas much of the surface is yellow or light greenish. (Accurate natural color renditions were not possible from the Voyager images taken during the 1979 flybys because there was no coverage in the red.) The reddish materials may be associated with very recent fragmental volcanic deposits (pyroclastics) erupted in the form of volcanic plumes. Dark materials appear in flows and on caldera floors. Bright white materials correspond to sulfur dioxide frost, and bright yellow materials appear to be in new flows such as those surrounding Ra Patera. The red material may be unstable since the color appears to fade over time. This fading appears to occur most rapidly in the equatorial region and more slowly over the polar regions; surface temperature may control the rate of transformation. Comparisons of these images to those taken by the Voyager spacecraft 17 years ago have revealed that many changes have occurred on Io. Since that time, about a dozen areas at least as large as the state of Connecticut have been resurfaced. Io's diameter is 3632 km.
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Telegonus Mensa in HR34 visteA cliff slumps outward in these HR view that NASA's Galileo spacecraft captured of the edge of a mountain named Telegonus Mensa on Jupiter's moon Io. When Galileo flew near the South Pole of Io in October 2001, scientist's targeted this cliff to study the process of erosion. Water and wind cause most erosion on Earth, but Io has neither surface water nor atmosphere. The cliff is slumping due to gravity (?). The picture has a resolution of about 10 mt (33 feet) per picture element. Galileo's camera took it from a distance of about 1000 Km (about 620 miles). North is to the top and the Sun illuminates the surface from the upper right.
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Frozen H2SO4 (Sulphuric Acid) on Europa?26 visteFrozen Sulfuric Acid on Jupiter's moon Europa is depicted in this image produced from data gathered by NASA's Galileo spacecraft. The brightest areas, where the yellow is most intense, represent Regions of high frozen Sulfuric Acid concentration. Sulfuric Acid is found in "exhaust battery acid" and in Earth's acid rain.
This image is based on data gathered by Galileo's NIMS (Near Infrared Mapping Spectrometer).
Europa's Leading Hemisphere is toward the bottom right and there are enhanced concentrations of Sulfuric Acid in the Trailing Side of Europa (the upper left side of the image). This is the face of Europa that is struck by sulfur ions coming from Jupiter's innermost moon, Io. The long, narrow features that criss-cross Europa also show Sulfuric Acid that may be from sulfurous material extruded in cracks.
Galileo, launched in 1989, has been orbiting Jupiter and its moons since December 1995.
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Old impact crater on Europa (from about 29.000 Km)32 visteThis feature on Europa was seen as a dark, diffuse circular patch on a previous Galileo global image of Europa's Leading Hemisphere on April 3, 1997. The "bulls-eye" pattern appears to be a 140- Km-wide impact scar (about the size of the island of Hawaii) which formed as the surface fractured minutes after a mountain-sized asteroid or comet slammed into the satellite. This approx. 214-Km-wide picture is the product of 3 images which have been processed in false color to enhance shapes and compositions. North is toward the top of this picture, which is illuminated from sunlight coming from the West. This color composite reveals a sequence of events which have modified the surface of Europa. The earliest event was the impact which formed the Tyre structure at 34° North Latitude and 146,5° West Longitude. The impact was followed by the formation of the reddish lines superposed on Tyre. The red color designates areas that are probably a dirty water ice mixture. The fine blue-green lines crossing the region from west to east appear to be ridges which formed after the crater.
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Fine details of Ganymede icy-surface28 visteDramatic 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.
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Frost on crater-tops of Ganymede25 visteScientists 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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Beautiful Europa...28 visteThis global view of Europa shows the location of a four-frame mosaic of images taken by NASA's Galileo spacecraft, set into low-resolution data obtained by the Voyager spacecraft in 1979. Putting new data into its surrounding context is a technique that allows scientists to better understand features observed on planetary surfaces. The Galileo spacecraft obtained these images during its first orbit of Jupiter at a distance of about 156.000 km (such approx. 96.300 miles) on June 27, 1996. The finest details that can discerned in this picture are about 1,6 Km (1 mile) across. North is to the top.
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Europa: computer mosaic from Voyager 224 visteEuropa looks like a cracked egg in this computer mosaic of the best Voyager 2 images. In this presentation, the variation of surface brightness due to the angle of the sun has been removed by computer processing, so that surface features can be seen equally well at all places. The many broad dark streaks show up well, but this presentation does not bring out the much fainter and more enigmatic light streaks. These pictures were taken from a distance of about 250.000 Km and show features as small as 5 Km across.
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Fresh features on Europa32 visteA newly discovered impact crater can be seen just right of the center of this image of Jupiter's moon Europa returned by NASA's Galileo spacecraft camera. The crater is about 30 kilometers (18.5 miles) in diameter. The impact excavated into Europa's icy crust, throwing debris (seen as whitish material) across the surrounding terrain. Also visible is a dark band, named Belus Linea, extending east-west across the image. This type of feature, which scientists call a 'triple band,' is characterized by a bright stripe down the middle. The outer margins of this and other triple bands are diffuse, suggesting that the dark material was put there as a result of possible geyser-like activity which shot gas and rocky debris from Europa's interior. The curving 'X' pattern seen in the lower left corner of the image appears to represent fracturing of the icy crust and infilling by slush which froze in place. The crater is centered at about 2 degrees north latitude by 239 degrees west longitude. The image was taken from a distance of 156,000 kilometers (about 96,300 miles) on June 27, 1996, during Galileo's first orbit around Jupiter. The area shown is 860 by 700 kilometers (530 by 430 miles), or about the size of Oregon and Washington combined.
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The typical "surface features" of Europa35 visteJupiter's moon Europa, as seen in this image taken June 27, 1996 by NASA's Galileo spacecraft, displays features in some areas resembling ice floes seen in Earth's polar seas. Europa, about the size of Earth's moon, has an icy crust that has been severely fractured, as indicated by the dark linear, curved, and wedged-shaped bands seen here. These fractures have broken the crust into plates as large as 30 kilometers (18.5 miles) across. Areas between the plates are filled with material that was probably icy slush contaminated with rocky debris. Some individual plates were separated and rotated into new positions. Europa's density indicates that it has a shell of water ice as thick as 100 kilometers (about 60 miles), parts of which could be liquid. Currently, water ice could extend from the surface down to the rocky interior, but the features seen in this image suggest that motion of the disrupted icy plates was lubricated by soft ice or liquid water below the surface at the time of disruption. This image covers part of the equatorial zone of Europa and was taken from a distance of 156,000 kilometers (about 96,300 miles) by the solid-state imager camera on the Galileo spacecraft. North is to the right and the sun is nearly directly overhead. The area shown is about 360 by 770 kilometers (220-by-475 miles or about the size of Nebraska), and the smallest visible feature is about 1.6 kilometers (1 mile) across.
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