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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As Time Goes By...On Io! (2)43 vistenessun commento
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As Time Goes By...On Io! (1)30 visteDetail of changes on Jupiter's moon Io in the Region around Volund as seen by the Voyager 1 spacecraft in April 1979 (left frame) and NASA's Galileo spacecraft in September 1996 (right frame). North is to the top of both frames which are approx. 600 by 600 Km. Note the new linear feature, which may be a volcanic fissure, trending east from the southern end of Volund. Dark diffuse material lies to the west and a ring of bright material which may be SO2- rich plume deposits appears to be centered near the middle of the new linear feature.
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Pele's deposits on Io34 visteThe varied effects of Ionian volcanism can be seen in this false color infrared composite image of Io's Trailing Hemisphere. LR color data from Galileo's first orbit (June, 1996) have been combined with a HR clear filter picture taken on the third orbit (November, 1996) of the spacecraft around Jupiter. A diffuse ring of bright red material encircles Pele, the site of an ongoing, high velocity volcanic eruption. Pele's plume is nearly invisible, except in back-lit photographs, but its deposits indicate energetic ejection of sulfurous materials out to distances more than 600 Km from the central vent. Another bright red deposit lies adjacent to Marduk, also a currently active ediface. High temperature hot spots have been detected at both these locations, due to the eruption of molten material in lava flows or lava lakes. Bright red deposits on Io darken and disappear within years or decades of deposition, so the presence of bright red materials marks the sites of recent volcanism.
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Pillan Patera23 visteThese images of Jupiter's volcanic moon, Io, show the results of a dramatic event that occurred on the fiery satellite during a five-month period. The changes, captured by the solid state imaging (CCD) system on NASA's Galileo spacecraft, occurred between the time Galileo acquired the left frame, during its seventh orbit of Jupiter, and the right frame, during its tenth orbit. A new dark spot, 400 kilometers (249 miles) in diameter, which is roughly the size of Arizona, surrounds a volcanic center named Pillan Patera. Galileo imaged a 120 kilometer (75 mile) high plume erupting from this location during its ninth orbit. Pele, which produced the larger plume deposit southwest of Pillan, also appears different than it did during the seventh orbit, perhaps due to interaction between the two large plumes. Pillan's plume deposits appear dark at all wavelengths. This color differs from the very red color associated with Pele, but is similar to the deposits of Babbar Patera, the dark feature southwest of Pele. Some apparent differences between the images are not caused by changes on Io's surface, but rather are due to differences in illumination, emission and phase angles. This is particularly apparent at Babbar Patera.
North is to the top of the images. The left frame was acquired on April 4th, 1997, while the right frame was taken on Sept. 19th, 1997. The images were obtained at ranges of 563,000 kilometers (350,000 miles) for the left image, and 505,600 kilometers (314,165 miles) for the right.
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Galai Patera28 visteIo's volcanic plains are shown in this Voyager 1 image, which spans an area about 1030 km (640 miles) from left to right. North is about the 1:30 position. Numerous volcanic calderas and lava flows are visible here. The brown teardrop-shaped feature at left center is Galai Patera, a 100-km-long (62 mi) lava-flooded caldera (collapsed vent) of a volcano. The composition of Io's volcanic plains and lava flows has not been determined. The prevalent yellow, brown, and orange material may consist dominantly of sulfur with surface frosts of sulfur dioxide or of silicates (such as basalt) encrusted with sulfur and sulfur dioxide condensates. The whitish patches probably are freshly deposited SO2 frost.
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Loki patera: an everlasting eruption...29 visteA huge area of Io's volcanic plains is shown in this Voyager 1 image mosaic. Numerous volcanic calderas and lava flows are visible here. Loki Patera, an active lava lake, is the large shield-shaped black feature. Heat emitted from Loki can be seen through telescopes all the way from Earth. These telescopic observations tell us that Loki has been active continuously (or at least every time astronomers have looked) since the Voyager 1 flyby in March 1979. The composition of Io's volcanic plains and lava flows has not been determined, but they could consist dominantly of Sulphur (S) with surface frosts of S dioxide or of silicates (such as basalts) encrusted with S and S dioxide condensates. The bright whitish patches probably consist of freshly deposited SO2 frost. The black spots, including Loki, are probably hot sulfur lava, which may remain molten by intrusions of molten silicate magma, coming up from deeper within Io. The ultimate source of heat that keeps Io active is tidal frictional heating due to the continual flexure of Io by the gravity of Jupiter and Europa, another of Jupiter's satellites.
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Io's "aurorae"33 visteThis eerie view of Jupiter's moon Io in eclipse (left) was acquired by NASA's Galileo spacecraft while the moon was in Jupiter's shadow. Gases above the satellite's surface produced a ghostly glow that could be seen at visible wavelengths (red, green and violet). The vivid colors, caused by collisions between Io's atmospheric gases and energetic charged particles trapped in Jupiter's magnetic field, had not previously been observed. The green and red emissions are probably produced by mechanisms similar to those in Earth's polar regions that produce the aurora, or northern and southern lights. Bright blue glows mark the sites of dense plumes of volcanic vapor, and may be places where Io is electrically connected to Jupiter. The viewing geometry is shown in the image on the right. North is to the top of the picture and Jupiter is on the right. The resolution is 13,5 Km (about 8 miles) per picture element. The images were taken on May 31, 1998 at a range of 1,3 MKM (such as about 800.000 miles) by Galileo's onboard solid state imaging camera system during the spacecraft's 15th orbit of Jupiter.
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Amalthea and Io (approx. true colors)104 visteComposite view of Amalthea and Io at the same scale. The visible part of Amalthea is about 150 Km across. The colors are just approximate. Amalthea is actually much darker than Io, but is displayed at a similar brightness for ease of viewing. The shape of Amalthea is controlled largely by impact cratering and fragmentation. In contrast, Io, like Earth, has gravity sufficient to form it into a slightly ellipsoidal sphere. Amalthea is covered by craters because there are no processes which erode or cover them efficiently. On extremely volcanically active Io, impact craters are covered quickly by lavas and other volcanic materials. Some of the volcanic materials escape from Io and probably contribute to the reddish colors of Amalthea and the other small inner satellites. The Amalthea and Io composites, obtained by the Solid State Imaging (SSI) camera on NASA's Galileo spacecraft on different orbits, were placed side by side for comparison purposes. The Amalthea composite combines data taken with the clear filter of the SSI system during orbit six, with lower resolution color images taken with the green, violet, and 1 micrometer filters during orbit 4. The Io data was obtained on July 2nd, 1998 (orbit 14) using the green, violet, and 1 micrometer filters.
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The Rings of Jupiter (1)32 visteOriginal caption:"This schematic cut-away view of the components of Jupiter's Ring System shows the geometry of the Rings in relation to Jupiter and to the small inner moons, which are the source of the dust forming the Rings themselves. The innermost and thickest Ring, shown in gray shading, is the halo that ends at the Main Ring. The thin, narrow Main Ring, shown with red shading, is bounded by the 16- Km-wide (10-miles) satellite Adrastea and shows a marked decrease in brightness near the orbit of Jupiter's innermost moon, Metis. It is composed of fine particles knocked off Adrastea and Metis. Although the orbits of Adrastea and Metis are about 1000 Km (about 600 miles) apart, that separation is not depicted in this drawing. Impacts by small meteoroids (fragments of asteroids and comets) into these small, low-gravity satellites feed material into the Rings. Thebe and Amalthea, the next 2 moons in increasing distance from Jupiter, supply dust which forms the thicker, disk-like 'Gossamer' Rings".
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The Rings of Jupiter (2)25 visteScientists studying data from Galileo spacecraft have found that the Ring System is made up of impact debris created when meteoroids, which are fragments of comets and asteroids, slam into Jupiter`s four smallest satellites. The top panel shows that the Main Ring (red) is formed mostly from meteoroid impact debris kicked up from the innermost moons, Metis (m) and Adrastea (a). Since both satellites orbit in paths not inclined to Jupiter's equator, the Main Ring appears as a narrow line. The middle panel shows the additional effect of dust ejected from the satellite Amalthea (A), responsible for producing 1 of the 2 moon components of the Gossamer Ring. Amalthea's orbit is inclined to Jupiter's equatorial plane and at different times the satellite's vertical position can range anywhere between the 2 extreme limits shown. Dust ejected from Amalthea (orange) produces a ring whose thickness equals Amalthea's vertical projections beyond Jupiter's equatorial plane. The lower panel shows the additional effect of dust ejected from Thebe (T), which makes up the second component (shown in green) of the gossamer ring. Again, the two positions shown represent the maximum projections of Thebe from Jupiter's equatorial plane. This component of the gossamer ring is thicker than the component due to Amaltheas dust because Thebe's orbit is more inclined than that of Amalthea.
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First look at Amalthea49 visteOriginal caption:"Galileo's first view of Amalthea, a small inner moon of Jupiter, showing the end of the elongated satellite that faces permanently toward the Giant Planet. North is to the top of the picture and the Sun illuminates the surface from the left. The circular feature that dominates the upper-right portion of the disk is Pan, the largest crater on Amalthea. This crater is about 90 Km wide. The bright spot at the South Pole is associated with another, slightly smaller crater named Gaea. (...) ".
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