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Technicians at the Jet Propu …
Description Technicians at the Jet Propulsion Laboratory ready the power and pyro subsystem for installation of NASA's Saturn-bound Cassini spacecraft. The work was one of many major milestones met in the Cassini program in January 1996. Cassini is scheduled for launch to Saturn in October 1997 and will arrive at the ringed planet in July 2004 to begin four years of detailed studies there. It will also carry a parachuted probe to be dropped to the surface of Saturn's large moon Titan. The Cassini mission is a joint effort of NASA, the European Space Agency and the Italian Space Agency.
Europa's Active Surface bw
A newly discovered impact cr …
8/13/96
Date 8/13/96
Description A 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. The Galileo mission is managed by NASA's Jet Propulsion Laboratory.
Io Triplet
Three full-disk color views …
8/13/96
Date 8/13/96
Description Three full-disk color views of Jupiter's volcanic moon Io as seen by NASA's Galileo spacecraft camera are shown in enhanced color (near-infrared-, green-, and violet-filtered images) to highlight details of the surface. Comparisons of these images to those taken by the Voyager spacecraft 17 years ago has revealed 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. These three views, taken by Galileo in late June 1996, show about 75 percent of Io's surface. The images reveal that some areas on Io are truly red, whereas much of the surface is yellow or light greenish. The major red areas shown here appear to be closely associated with very recent fragmental volcanic deposits (pyroclastics) erupted in the form of volcanic plumes. The most prominent red oval surrounds the volcano Pele (far right), as previously discovered by Hubble Space Telescope images. An intense red spot lies near the active plume Marduk east of Pele. Other reddish areas are associated with known hot spots or regions that have changed substantially since the Voyager spacecraft flybys of 1979. The reddish deposits may be the products of high-temperature explosive volcanism. There are some curious differences in the overlap region between the images at left and center. There are several especially bright areas in the image at left that appear much darker in the image at center. These may represent transient eruptions or surface materials with unusual light-scattering properties. Several volcanic plumes active during the Voyager flybys in 1979 occurred near the bright limbs or terminator regions of these images, where airborne materials should be detectable. Loki and Amirani appear to be inactive, Volund is active, and Pele may be active but is extremely faint. The plume Marduk also seems to be active, and dark jets of erupting materials can be seen against the disk. Several previously unknown mountains can be seen near the terminators. The Galileo mission is managed by NASA's Jet Propulsion Laboratory.
Dark Bands on Europa
Dark crisscrossing bands on …
8/13/96
Date 8/13/96
Description Dark crisscrossing bands on Jupiter's moon Europa represent widespread disruption from fracturing and the possible eruption of gases and rocky material from the moon's interior in this four-frame mosaic of images from NASA's Galileo spacecraft. These and other features suggest that soft ice or liquid water was present below the ice crust at the time of disruption. The data do not rule out the possibility that such conditions exist on Europa today. The pictures were taken from a distance of 156,000 kilometers (about 96,300 miles) on June 27, 1996. Many of the dark bands are more than 1,600 kilometers (1,000 miles) long, exceeding the length of the San Andreas fault of California. Some of the features seen on the mosaic resulted from meteoritic impact, including a 30-kilometer (18.5 mile) diameter crater visible as a bright scar in the lower third of the picture. In addition, dozens of shallow craters seen in some terrains along the sunset terminator zone (upper right shadowed area of the image) are probably impact craters. Other areas along the terminator lack craters, indicating relatively youthful surfaces, suggestive of recent eruptions of icy slush from the interior. The lower quarter of the mosaic includes highly fractured terrain where the icy crust has been broken into slabs as large as 30 kilometers (18.5 miles) across. The mosaic covers a large part of the northern hemisphere and includes the north pole at the top of the image. The sun illuminates the surface from the left. The area shown is centered on 20 degrees north latitude and 220 degrees west longitude and is about as wide as the United States west of the Mississippi River. The Galileo mission is managed by NASA's Jet Propulsion Laboratory.
Eruption on Io
This image, taken by NASA's …
8/13/96
Date 8/13/96
Description This image, taken by NASA's Galileo spacecraft, shows a new blue- colored volcanic plume extending about 100 kilometers (about 60 miles) into space from Jupiter's moon Io (see inset at lower left). The blue color of the plume is consistent with the presence of sulfur dioxide gas and "snow" condensing from the gas as the plume expands and cools. Galileo images have also shown that the Ra Patera plume glows in the dark, perhaps due to the fluorescence of sulfur and oxygen ions created by the breaking apart of sulfur dioxide molecules by energetic particles in the Jovian magnetosphere. The images at right show a comparison of changes seen near the volcano Ra Patera since the Voyager spacecraft flybys of 1979 (windows at right show Voyager image at top and Galileo image at bottom). This eruptive plume is an example of a new type of volcanic activity discovered during Voyager's flyby in 1979, believed to be geyser- like eruptions driven by sulfur dioxide or sulfur gas erupting and freezing in Io's extremely tenuous atmosphere. Volcanic eruptions on Earth cannot throw materials to such high altitudes. Ra Patera is the site of dramatic surface changes. An area around the volcano of about 40,000 square kilometers, area about the size of New Jersey, has been covered by new volcanic deposits. The image was taken in late June 28, 1996 from a distance of 972,000 kilometers (604,000 miles). The Galileo mission is managed by NASA's Jet Propulsion Laboratory.
Europa, Callisto and Jupiter
One moment in an ancient, or …
12/21/00
Date 12/21/00
Description One moment in an ancient, orbital dance is caught in this color picture taken by NASA's Cassini spacecraft on Dec. 7, 2000, just as two of Jupiter's four major moons, Europa and Callisto, were nearly perfectly aligned with each other and the center of the planet. The distances are deceiving. Europa, seen against Jupiter, is 600,000 kilometers (370,000 miles) above the planet's cloud tops. Callisto, at lower left, is nearly three times that distance from the cloud tops. Europa is a bit smaller than Earth's Moon and has one of the brightest surfaces in the solar system. Callisto is 50 percent bigger -- roughly the size of Saturn's largest satellite, Titan -- and three times darker than Europa. Its brightness had to be enhanced in this picture, relative Europa's and Jupiter's, in order for Callisto to be seen in this image. Europa and Callisto have had very different geologic histories but share some surprising similarities, such as surfaces rich in ice. Callisto has apparently not undergone major internal compositional stratification, but Europa's interior has differentiated into a rocky core and an outer layer of nearly pure ice. Callisto's ancient surface is completely covered by large impact craters: The brightest features seen on Callisto in this image were discovered by the Voyager spacecraft in 1979 to be bright craters, like those on our Moon. In contrast, Europa's young surface is covered by a wild tapestry of ridges, chaotic terrain and only a handful of large craters. Recent data from the magnetometer carried by the Galileo spacecraft, which has been in orbit around Jupiter since 1995, indicate the presence of conducting fluid, most likely salty water, inside both Callisto and Europa. Scientists are eager to discover whether the surface of Saturn's Titan resembles that of Callisto or Europa, or whether it is entirely different, when Cassini finally reaches its destination in 2004. Cassini is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini mission for NASA's Office of Space Science, Washington, D.C. Credit: NASA/JPL/University of Arizona #####
Io's Atmosphere & Volcanoes
The atmosphere and volcanic …
12/30/00
Date 12/30/00
Description The atmosphere and volcanic hotspots of Jupiter's moon Io are apparent in this view of the moon in eclipse, taken by NASA's Galileo spacecraft. Galileo is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Office of Space Science, Washington, D.C.
This is a composite of two i …
1/17/97
Date 1/17/97
Description This is a composite of two images of Jupiter's icy moon Europa obtained from a range of 2119 miles (3410 kilometers) by the Galileo spacecraft during its fourth orbit around Jupiter and its first close pass of Europa. The mosaic spans 11 miles by 30 miles (17 km by 49 km) and shows features as small as 230 feet (70 meters) across. This mosaic is the first very high resolution image data obtained of Europa, and has a resolution more than 50 times better than the best Voyager coverage and 500 times better than Voyager coverage in this area. The mosaic shows the surface of Europa to be structurally complex. The sun illuminates the scene from the right, revealing complex overlapping ridges and fractures in the upper and lower portions of the mosaic, and rugged, more chaotic terrain in the center. Lateral faulting is revealed where ridges show offsets along their lengths (upper left of the picture). Missing ridge segments indicate obliteration of pre-existing materials and emplacement of new terrain (center of the mosaic). Only a small number of impact craters can be seen, indicating the surface is not geologically ancient. The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC. This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://www.jpl.nasa.gov/galileo. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo #####
NASA's search for life elsew …
8/25/98
Date 8/25/98
Description NASA's search for life elsewhere in the solar system is bringing space scientists to the giant kelp forest exhibit at the Monterey Bay Aquarium to test a new scientific probe that might one day look for life in oceans that may exist on Jupiter's icy moon Europa. In this picture, a Diver deploys the JPL probe in the kelp forest exhibit at the Monterey Bay Aquarium.
Sulfuric Acid on Europa
Frozen sulfuric acid on Jupi …
9/1/99
Date 9/1/99
Description Frozen 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 battery acid and in Earth's acid rain. This image is based on data gathered by Galileo's 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 crisscross 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. JPL manages the Galileo mission for NASA's Office of Space Science, Washington DC. JPL is a division of the California Institute of Technology, Pasadena, CA. #####
Eyeing Ganymede
Jupiter casts a baleful eye …
12/5/00
Date 12/5/00
Description Jupiter casts a baleful eye toward the moon Ganymede in this enhanced-contrast image from NASA's Cassini spacecraft. Jupiter's `eye', the Great Red Spot, was captured just before disappearing around the eastern edge of the planet. The furrowed eyebrow above and to the left of the spot is a turbulent wake region caused by westward flow that has been deflected to the north and around the Red Spot. The smallest features visible are about 240 kilometers (150 miles) across. Within the band south of the Red Spot are a trio of white ovals, high pressure counterclockwise-rotating regions that are dynamically similar to the Red Spot. The dark filamentary features interspersed between white ovals are probably cyclonic circulations and, unlike the ovals, are rotating clockwise. Jupiter's equatorial zone stretching across the planet north of the Spot appears bright white, with gigantic plume clouds spreading out from the equator both to the northeast and to the southeast in a chevron pattern. This zone looks distinctly different than it did during the Voyager flyby 21 years ago. Then, its color was predominantly brown and the only white plumes conspicuous against the darker material beneath them were oriented southwest-to-northeast. Ganymede is Jupiter's largest moon, about 50 percent larger than our own Moon and larger than the planet Mercury. The visible details in this image are different geological terrains. Dark areas tend to be older and heavily cratered, brighter areas are younger and less cratered. Cassini images of Ganymede and Jupiter's other large moons taken near closest approach on Dec. 30 will have resolutions about four times better than that seen here. This image is a color composite of ones taken with different filters by Cassini's narrow-angle camera on Nov. 18, 2000, processed to enhance contrast. Cassini is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini mission for NASA's Office of Space Science, Washington, D.C. Credit: NASA/JPL/University of Arizona # # # # #
Cassini Spacecraft Fully Ass …
The fully assembled Cassini …
2/20/97
Date 2/20/97
Description The fully assembled Cassini spacecraft as it appeared Feb. 14, 1997 in JPL's spacecraft assembly facility in Pasadena, CA. The spacecraft is scheduled for launch on its mission to Saturn on Oct. 6, 1997 from Cape Canaveral, FL. Having successfully completed testing in JPL's space simulator, the spacecraft is now undergoing a final round of systems testing prior to shipment this spring to NASA's Kennedy Space Center in Florida for launch preparations. Cassini's mission is to orbit Saturn for four years and study the planet, its rings and moons in detail. The large moon Titan is a principal target for exploration, and Cassini will carry the Huygens probe, seen here mounted on the side of the spacecraft (at left), to be released to enter Titan's thick atmosphere and descend to the surface via parachute. The Huygens probe is provided by the European Space Agency (ESA) and the radio antenna at top was provided by the Italian Space Agency (ASI). The Cassini mission is a joint endeavor of NASA, ESA and ASI. JPL manages the Cassini program for NASA's Office of Space Science, Washington, D.C. #####
Europa Triple Band
This picture of Europa, a mo …
4/9/97
Date 4/9/97
Description This picture of Europa, a moon of Jupiter, was obtained on February 20, 1997, by the Solid State Imaging system onboard the Galileo spacecraft during its sixth orbit around Jupiter. The area is centered at 9.3 degrees north latitude, 275.7 degrees west longitude, on the trailing hemisphere of Europa. As Europa moves in its orbit around Jupiter, the trailing hemisphere is the portion which is always on the moon's backside opposite to its direction of motion. The area depicted is about 32 kilometers by 40 kilometers (20 miles by 25 miles). Resolution is 54 meters (59 yards). The Sun illuminates the scene from the right (east). A section of a triple band crosses the upper left of the picture and extends for hundreds of miles across the surface. Triple bands derive their name from their appearance at lower resolution as a narrow bright band flanked by a pair of darker bands. At the high resolution of this picture, however, the triple band is much more complex and is composed of a system of ridges 6 kilometers (4 miles) across. Some ridges reach heights of about 180 meters (200 yards). Other features include a hill in the center of the picture about 480 meters (500 yards) high. Two mounds about 6 kilometers across (4 miles) are seen in the bottom of the picture. The ridges, hills and mounds probably all represent uplifts of the icy crust of Europa by processes originating from the interior. The Jet Propulsion Laboratory, Pasadena, CA, manages the mission for NASA's Office of Space Science, Washington D.C. This image and other images and data received from Galileo are posted on the World Wide Web Galileo mission home page at: http://www.jpl.nasa.gov/galileo. #####
Close-up of Europa's Surface
This close-up view of the ic …
4/11/97
Date 4/11/97
Description This close-up view of the icy surface of Europa, a moon of Jupiter, was obtained on December 20, 1996, by the Solid State Imaging system on board the Galileo spacecraft during its fourth orbit around Jupiter. The view is about 13 kilometers by 18 kilometers (8 miles by 11 miles) and has a resolution of 26 meters (28 yards). The Sun illuminates the scene from the east (right). A flat smooth area about 3.2 kilometers (2 miles) across is seen in the left part of the picture. This area resulted from flooding by a fluid which erupted onto the surface and buried sets of ridges and grooves. The smooth area contrasts with a distinctly rugged patch of terrain farther east, to the right of the prominent ridge system running down the middle of the picture. The rugged patch of terrain is 4 kilometers (2.5 miles) across and represents localized disruption of the complex network of ridges in the area. Eruptions of material onto the surface, crustal disruption, and the formation of complex networks of folded and faulted ridges show that significant energy was available in the interior of Europa. Although small impact craters are most easily seen in the smooth area, they occur throughout the ridged terrain seen in this view. The Jet Propulsion Laboratory, Pasadena, CA, manages the mission for NASA's Office of Space Science, Washington D.C. This image and other images and data received from Galileo are posted on the World Wide Web Galileo mission home page at: http://www.jpl.nasa.gov/galileo. #####
Himalia, a Small Moon of Jup …
NASA's Cassini spacecraft ca …
1/23/01
Date 1/23/01
Description NASA's Cassini spacecraft captured images of Himalia, the brightest of Jupiter's outer moons, on Dec. 19, 2000, from a distance of 4.4 million kilometers (2.7 million miles). This near-infrared image, with a resolution of about 27 kilometers (17 miles) per pixel, indicates that the side of Himalia facing the spacecraft is roughly 160 kilometers (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. Cassini is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini mission for NASA's Office of Space Science, Washington, D.C. Credit: NASA/JPL/University of Arizona # # # # #
Galilean Moon Interiors
This artist's concept shows …
6/4/98
Date 6/4/98
Description This artist's concept shows cross-sections of the four largest moons of Jupiter, with the interior structures based on the latest information sent back by NASA's Galileo spacecraft. The moons depicted are (clockwise from bottom right) Callisto, Ganymede, Io and Europa. Scientists have modified their concept of Callisto's interior, based on the most recent Galileo findings. Whereas previously they believed that Callisto was completely undifferentiated, with a uniform mixture of rock and ice, scientists now say the interior has some separation of the ice and rock, but not nearly as much as the other three moons. Galileo data indicate that Ganymede is separated into a metallic core, rock mantle, and ice-rich outer shell, while Io has a metallic core and rock mantle, but no ice. Galileo data has also helped scientists refine their model of Europa's structure. They believe Europa has a metallic core surrounded by a rock mantle and a water ice-liquid outer shell. The core may be up to half the size of Europa's radius, with the water ice-liquid shell estimated to be between 80 to 170 kilometers thick (50 to 106 miles), with 100 kilometers (62 miles) considered the most likely thickness. Information on the interior structure of the four moons was obtained by studying radio Doppler data that is gathered when Galileo flies by the satellites. Each moon exerts a gravitational tug, but the tug's strength is determined by how much rock is contained within the moon (the higher the rock content, the stronger the tug). The tug changes the spacecraft's speed and the radio frequency of its signals. Scientists study those changes to determine the rock content and structure of the moon. This material was presented to the American Astronomical Society meeting in San Diego, CA on June 4, 1998. The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is a division of California Institute of Technology (Caltech). This image, along with other images and data received from Galileo, is available on the Galileo mission home page at http://www.jpl.nasa.gov/galileo. Background information and educational context for the images can be found at http://www.jpl.nasa.gov/galileo/sepo . #####
A Digital Video Disk (DVD) b …
8/21/97
Date 8/21/97
Description A Digital Video Disk (DVD) bearing 616,400 digitized signatures of people from nations around the world has been attached to the Cassini spacecraft and will soon be on its way to Saturn. The disk cover, designed by Cassini science and engineering manager Charley Kohlhase, shows the flags from 28 of the 81 nations whose citizens sent signatures for the chance to send their names into space. The planet Saturn with its rings and its moon Titan and the Earth are also represented, as is the Cassini spacecraft and its Huygens probe. The feathers represent the Golden Eagle, whose feathers were used as quills for writing to spread wisdom. The bird is revered in mythology for carrying spirits above the Earth to the heavens. The flags, going clockwise from the American flag top center, are in order of the number of signatures collected, with the highest number from the United States. The disk is fitted into a shallow cavity between two pieces of aluminum that will protect it from micrometeoroid impacts. The package will be mounted to the side of the 2-story- tall spacecraft beneath a pallet carrying cameras and other science instruments that will be used to study the Saturnian system. A specially designed, multicolored patch of thermal blanket material will be installed over the disk package. Along with the spacecraft, the disk will reside in Saturn's orbit centuries after the primary mission is completed in July 2008. The Cassini mission is managed for NASA's Office of Space Science, Washington, D.C., by the Jet Propulsion Laboratory, a division of the California Institute of Technology. #####
Europa--Ice Rafting
A small region of the thin, …
12/16/97
Date 12/16/97
Description A small region of the thin, disrupted ice crust in the Conamara region of Jupiter's moon Europa shows the interplay of surface color with ice structures in this image produced with data from NASA's Galileo spacecraft camera. The white and blue colors outline areas that have been blanketed by a fine dust of ice particles ejected when an explosive impact created the large crater Pwyll (26 kilometers or 16 miles in diameter) located some 1,000 kilometers (about 620 miles) to the south. Also visible are a few small craters of less than 500 meters or 547 yards in diameter that were probably formed at the same when the impact likely threw out large, intact, blocks of around the area. The unblanketed surface has a reddish brown color that has been painted by mineral contaminants carried and spread by water vapor released from below the crust when it was disrupted. The original color of the icy surface was probably a deep blue seen in large areas elsewhere on Europa's surface. The colors in this picture have been enhanced for visibility. North is to the top of the picture and the Sun illuminates the surface from the right. The image, centered at 9 degrees latitude and 86.5 degrees south longitude, covers an area approximately 70 by 30 kilometers (44 by 19 miles), and combines data taken by the Galileo Solid State Imaging (CCD) system during three of the spacecraft's orbits through the Jovian system. Low- resolution color (violet, green, and infrared) data acquired in September 1996 were combined with medium-resolution images from December 1996 to produce synthetic color images. These were then combined with a high-resolution mosaic of images acquired on Feb. 20, 1997 at a resolution of 54 meters (59 yards) per picture element and at a range of 5,340 kilometers (3,320 miles). The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is a division of California Institute of Technology. This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://www.jpl.nasa.gov/galileo. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo #####
High-Resolution Europa Mosai …
This mosaic of images from N …
12/16/97
Date 12/16/97
Description This mosaic of images from NASA's Galileo spacecraft camera shows some of the highest resolution images of Jupiter's moon Europa ever acquired. The hundreds of ridges that cut across each other indicate multiple episodes of ridge formation either by volcanic or tectonic activity within the ice. The images were taken on Nov. 6, 1997 from a range of about 3,250 kilometers (about 1,990 miles). North is to the top of the image and the Sun illuminates the scene from the left. Also visible in the image are numerous isolated mountains or "massifs". The highest of these, located in the upper right corner and lower center of the mosaic, are approximately 500 meters (1,640 feet) high. Irregularly shaped areas where the ice surface appears to be lower than the surrounding plains (in the left-center and lower left corner of the mosaic) may be related to the chaotic areas of iceberg-like features seen in earlier Galileo images of Europa. The mosaic, centered at 35.4 degrees north latitude and 86.8 degrees west longitude, covers an area of 66 by 55 kilometers (108 by 90 miles). The smallest distinguishable features in the image are about 68 meters (223 feet) across. The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is a division of California Institute of Technology. This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://www.jpl.nasa.gov/galileo. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo #####
Regional Mosaic--Europa Chao …
This mosaic of images taken …
12/16/97
Date 12/16/97
Description This mosaic of images taken by NASA's Galileo spacecraft camera shows a region of Jupiter's moon Europa that is characterized by dark and splotchy-looking terrain -- evidence of some of the most recent geologic activity on Europa. The mottled appearance results from chaotic areas where the bright, icy crust has broken apart to expose a darker material underneath. North is to the top of the image, and the Sun illuminates the scene from the right. The images were taken on Nov. 6. The smooth gray band at the lower part of image represents a zone where the Europan crust has been fractured, separated, and filled in with material from the interior. The chaotic terrain and the gray band show that Europa has been subjected to intense geological deformation. The mosaic is centered at 2.9 degrees south latitude and 234.1 degrees west longitude and covers an area of 261 kilometers by 168 kilometers (159 miles by 102 miles). The smallest distinguishable features in the image are about 229 meters (751 feet) across. These images were obtained on Nov. 6, 1997, when the Galileo spacecraft was approximately 21,700 kilometers (about 13,240 miles) from Europa. The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is a division of California Institute of Technology. This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://www.jpl.nasa.gov/galileo. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo #####
Jupiter's Main Ring and Halo
The top and bottom panels sh …
9/15/98
Date 9/15/98
Description The top and bottom panels show a mosaic of images of Jupiter's rings taken by NASA's Galileo spacecraft. Jupiter is to the right of this mosaic, and different brightness scales accent different parts of the ring system. Jupiter's ring system has three parts -- a flat main ring, a halo inside the main ring shaped like a double-convex lens, and the gossamer ring outside the main ring. In the top view, a faint mist of particles is seen above and below the main rings. This vertically extended "halo" is unusual in planetary rings, and is caused by electromagnetic forces pushing the smallest grains, which carry electric charges, out of the ring plane. Jupiter's main ring is a thin sheet of material encircling the planet. The near and far arms of this ring extend horizontally across the mosaic, joining together at the ring's ansa, the portion visible on the sides of Jupiter, on the figure's far left side. In the bottom view, some radial structure is visible across the ring's ansa. The diffuse innermost boundary begins at approximately 122,500 kilometers (about 76,100 miles). The main ring's outer radius is at about 128,940 kilometers (80,120 miles), very close to the orbit of the Jovian moon Adrastea (128,980 kilometers or 80,140 miles). The brightness of the main ring drops markedly at about 127,850 kilometers (79,440 miles), very near the orbit of another moon, Metis, at 127,978 kilometers (79,521 miles). Jupiter's four small satellites-Metis, Adrastea, Amalthea and Thebe, affect the structure of the huge planet's tenuous rings. These images were taken through the clear filter of Galileo's onboard solid state imaging camera system on November 9, 1996. The resolution is approximately 24 kilometers (14 miles) per picture element along Jupiter's rings. Because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened vertically. The images were obtained when Galileo was in Jupiter's shadow, peering back toward the Sun, when the ring was approximately 2.3 million kilometers (1.4 million miles) away. The view of Earth's moon in the explanatory graphics was created from images returned by the Clementine lunar orbiter, launched in 1994 by NASA and the Ballistic Missile Defense Organization.) JPL manages the Galileo mission for NASA's Office of Space Science, Washington, DC. The images are posted on the Internet at http://photojournal.jpl.nasa.gov/ and at http://www.jpl.nasa.gov/galileo . Background information and educational context for the images can be found at: http://www.jpl.nasa.gov/galileo/sepo . ##### 9/9/98 JP
GLL/EM15
This mosaic picture of the M …
12/22/92
Date 12/22/92
Description This mosaic picture of the Moon was compiled from 18 images taken with a green filter by Galileo's imaging system during the spacecraft's flyby on December 7, 1992, some 11 hours before its Earth flyby at 1509 UTC (7:09 a.m. Pacific Standard Time) December 8. The north polar region is near the top part of the mosaic, which also shows Mare Imbrium, the dark area on the left, Mare Serenitatis at center, and Mare Crisium, the circular dark area to the right. Bright crater rim and ray deposits are from Copernicus, an impact crater 96 kilometers (60 miles) in diameter. Computer processing has exaggerated the brightness of poorly illuminated features near the day/night terminator in the polar regions, giving a false impression of high reflectivity there. The digital image processing was done by DLR the German aerospace research establishment near Munich, an international collaborator in the Galileo mission. The Galileo project, whose primary mission is the exploration of the Jupiter system in 1995-97, is managed for NASA's Office of Space Science and Applications by the Jet Propulsion Laboratory. #####
Jupiter's Main and Gossamer …
The schematic structures of …
9/15/98
Date 9/15/98
Description The schematic structures of Jupiter's main and gossamer rings are depicted here. Scientists studying data from NASA's 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 one of the two 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 two 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 Amalthea's dust because Thebe's orbit is more inclined than that of Amalthea. The Jupiter image was created from a map based on data obtained by the Hubble Space Telescope. The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL manages the Galileo mission for NASA's Office of Space Science, Washington, DC. The images are posted on the Internet at http://photojournal.jpl.nasa.gov/ and at http://www.jpl.nasa.gov/galileo . Background information and educational context for the images can be found at: http://www.jpl.nasa.gov/galileo/sepo . ##### 9/9/98 JP
GLL/EM16
This view looking down on th …
Description This view looking down on the north pole of the Moon was assembled from 18 images taken with a green filter by Galileo's imaging system as the spacecraft flew by the Moon on December 7, 1992. The part of the moon visible from Earth is toward the left and includes the dark, lava-filled Imbrium basin, upper left, Mare Serenitatis, middle left, Mare Tranquillitatis, lower left, and Crisium, the dark circular feature toward the bottom of the mosaic. Also visible in this view are the dark lava plains of the Marginis and Smythii basins, lower right. The Humboldtianum Basin, a 650-kilometer (400-mile) impact structure partly filled with dark volcanic deposits, is visible in the middle of the image. The Moon's north pole is located just inside the shadow zone about a third of the way from the top left of the lighted region. The Galileo project, whose primary mission is the exploration of the Jupiter system in 1995-97, is managed for NASA's Office of Space Science and Applications by the Jet Propulsion Laboratory. #####
GLL/EM17
This false-color mosaic was …
12/22/92
Date 12/22/92
Description This false-color mosaic was constructed from a series of 53 images taken through three spectral filters by Galileo's imaging system as the spacecraft flew over the northern regions of the Moon on December 7, 1992. The part of the Moon vlsible from Earth is on the left side in this view. The color mosaic shows compositional variations in parts of the Moon's northern hemisphere. Bright pinkish areas are highlands materials, such as those surrounding the oval lava-filled Crisium impact basin toward the bottom of the picture. B1ue to orange shades indicate volcanic lava flows. To the left of Crisium, the dark blue Mare Tranquillitatis is richer in titanium than the green and orange maria above it. Thin mineral-rich soils associated with relatively recent impacts are represented by light blue colors, the youngest craters have prominent blue rays extending from them. The Galileo project, whose primary mission is the exploration of the Jupiter system in 1995-97, is managed for NASA's Office of Space Science and Applications by the Jet Propulsion Laboratory. #####
GALILEO
This image is the most detai …
6/22/94
Date 6/22/94
Description This image is the most detailed picture of the recently discovered natural satellite of asteroid 243 Ida taken by the Galileo Solid-State Imaging camera during its encounter with the asteroid on August 28, 1993. Shuttered through the camera's broadband clear filter as part of a 30-frame mosaic designed to image the asteroid itself, this frame fortuitously captured the previously unknown moon at a range of about 3,900 kilometers (2,400 miles), just over 4 minutes before the spacecraft's closest approach to Ida. Each picture element spans about 39 meters (125 feet) on the surface of the moon. More than a dozen craters larger than 80 meters (250 feet) in diameter are clearly evident, indicating that the moon has suffered numerous collisions from smaller Solar System debris during its history. The larger crater on the terminator is about 300 meters (1,000 feet) across. The satellite is approximately egg-shaped, measuring about 1.2 x 1.4 x 1.6 kilometers (0.75 x 0.87 x 1 mile). At the time this image was shuttered, Ida was about 90 kilometers (56 miles) away from the moon, outside this frame to the left and slightly below center. This image was relayed to Earth from Galileo on June 8, 1994. The Galileo project, whose primary mission is the exploration of the Jupiter system in 1995-97, is managed for NASA's Office of Space Science by the Jet Propulsion Laboratory. #####
Bright Streak on Amalthea
These two images of Jupiter' …
4/24/00
Date 4/24/00
Description These two images of Jupiter's small, irregularly shaped moon Amalthea, obtained by the camera onboard NASA's Galileo spacecraft in August 1999 (left) and November 1999 (right), form a "stereo pair" that helps scientists determine this moon's shape and the topography of its surface features. Features as small as 3.8 kilometers (2.4 miles) across can be resolved in these images, making them among the highest-resolution images ever taken of Amalthea. The large impact crater visible in both images, near the right-hand edge of Amalthea's disk, is about 40 kilometers (about 29 miles) across, two ridges, tall enough to cast shadows, extend from the top of the crater in a V-shape reminiscent of a "rabbit ears" television antenna. To the left of these ridges, in the top center portion of Amalthea's disk, is a second large impact crater similar in size to the first crater. To the left of this second crater is a linear streak of relatively bright material about 50 kilometers (31 miles) long. In previous spacecraft images of Amalthea taken from other viewing directions, this bright feature was thought to be a small, round, bright "spot" and was given the name Ida. These new images reveal for the first time that Ida is actually a long, linear streak. This bright streak may represent material ejected during the formation of the adjacent impact crater, or it may just mark the crest of a local ridge. Other patches of relatively bright material can be seen elsewhere on Amalthea's disk, although none of these other bright spots has Ida's linear shape. In both images, sunlight is coming from the left and north is approximately up. Note that the north pole of Amalthea is missing in the right-hand image (it was cut off by the edge of the camera frame). The bright streak, Ida, is on the side of the moon that faces permanently away from Jupiter, and the crater near the right-hand edge of the disk is in the center of Amalthea's leading side (the side of the moon that "leads" as Amalthea moves in its orbit around Jupiter). The images are, from left to right: Amalthea taken on August 12, 1999 at a range of 446,000 kilometers (about 277,000 miles) and on November 26, 1999 at a range of 374,000 kilometers (about 232,000 miles). # # # # #
Highest resolution of lava f …
Lava flows similar to those …
4/19/00
Date 4/19/00
Description Lava flows similar to those found in Hawaii are seen in the black and white image at top, taken by NASA's Galileo spacecraft. It is one of the highest resolution images (7 meters or 23 feet per picture element) ever obtained of Jupiter's volcanic moon Io. The two horizontal black stripes are places where data were lost during transmission to Earth. The image shows the textures of lava flows on the floor of the caldera Chaac, which is shown in false color at lower resolution (185 meters or 607 feet per pixel element) in the bottom image. Calderas are depressions caused by collapse during volcanic eruptions. The one shown here is approximately 100 kilometers (63 miles) long and 30 kilometers (19 miles) across. Using shadow lengths from the new high-resolution observations, the northeastern (upper right) scarp, or line of cliffs, has been estimated to be 2.8 kilometers (9200 feet) high. The lava flows are similar in texture to lava flows within the caldera at Hawaii's Kilauea volcano. This suggests that the floor of Chaac has been covered by a combination of lava flows and lava lakes. The light-colored material surrounding the caldera may be composed of sulfur-dioxide frost or some other sulfur-rich material on the surface of Io. Galileo scientists believe that the greenish color on the caldera floor is a form of contaminated sulfur created when sulfur-rich material escaping from volcanic vents reacts chemically with warm lava flows. The high- resolution view shows numerous lava flows. The darkest flows are thought to be the most recent because they have not been covered by the sulfurous materials which coat most of Io's surface. The top image was acquired by Galileo on February 22, 2000. It was taken at a distance of 600 kilometers (370 miles) and is centered at 11.9 degrees north latitude and 157.6 degrees west longitude. North is to the top, and the Sun illuminates the surface from the right. The color image was created by combining a black and white image taken on February 22, 2000 at a distance of 18,800 kilometers (11,700 miles) from Io with lower-resolution (1.3 kilometers or 0.81 miles per picture element) color images taken on July 3, 1999 at a distance of 130,000 kilometers (81,000 miles). The image is centered at 11.6 degrees north latitude and 157.7 degrees west longitude. North is to the top and the Sun illuminates the surface from the left. The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is a division of the California Institute of Technology, Pasadena, CA. This image and other images and data received from Galileo are posted on the Galileo mission home page at http://galileo.jpl.nasa.gov . Background information and educational context for the images can be found at http://galileo.jpl.nasa.gov/images/io/ioimages.html . #####
Terrain near Io's south pole
Volcanic calderas, lava flow …
4/19/00
Date 4/19/00
Description Volcanic calderas, lava flows and cliffs are seen in this false color image of a region near the south pole of Jupiter's volcanic moon Io. It was created by combining a black and white image taken by NASA's Galileo spacecraft on February 22, 2000 with lower resolution color images taken by Galileo on July 3, 1999. The three black spots (top center and middle left) are small volcanic calderas about 10-20 kilometers (6-12 miles) in size, which are dark because their floors are covered by recent lava flows. Two of these three calderas are surrounded by diffuse dark material, which may have been thrown out of the calderas by explosive eruptions. The bright, white material is thought to be sulfur-dioxide frost and is concentrated near the cliffs in this image. It may be formed when liquid sulfur dioxide seeps out at the base of mountain scarps, vaporizes into a plume of gas, liquid and solid, and then condenses again on the surface. Part of this process, called sapping, occurs in arid environments on Earth when ground water seeps out at the bases of cliffs. The vaporization and production of plumes is much more dramatic on Io due to the lower gravitational acceleration and especially the very low atmospheric pressure. It may be one of the dominant erosion processes on Io. The mountain at the center left, named Telegonus Mensae, exhibits a number of ridges parallel to its margins. These ridges have been observed on a number of other Ionian mountains and they suggest that as the mountain ages, it is collapsing outward under the influence of gravity. The yellow lava flow at the southern end of the image appears to be fed by a dark channel that connects to a dark caldera. This is a likely candidate for a lava flow composed of sulfur (rather than silicate material). The image is centered at 53.8 degrees south latitude and 117.1 degrees west longitude and north is to the top. The higher resolution image has a resolution of 350 meters (or yards) per picture element and is illuminated from the upper left. It was taken at a range of 34,000 kilometers (21,000 miles). The color images have resolutions of 1.3 kilometers (0.81 miles) per picture element and are illuminated from almost directly behind the spacecraft. They were taken at a distance of about 130,000 kilometers (81,000 miles) by Galileo's onboard camera. The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is a division of the California Institute of Technology, Pasadena, CA. This image and other images and data received from Galileo are posted on the Galileo mission home page at http://galileo.jpl.nasa.gov . Background information and educational context for the images can be found at http://galileo.jpl.nasa.gov/images/io/ioimages.html . #####
Eruption at Tvashtar Catena, …
NASA's Galileo spacecraft ca …
5/18/00
Date 5/18/00
Description NASA's Galileo spacecraft caught this volcanic eruption in action on Jupiter's moon Io on November 25, 1999. This mosaic shows Tvashtar Catena, a chain of calderas, in enhanced color. It combines low resolution (1.3 kilometers, or .8 miles, per picture element) color images of Io taken on July 3, 1999 with the much higher resolution (180 meters, or 197 yards, per picture element) black and white images taken in November. The molten lava was hot enough, and therefore bright enough, to saturate, or overexpose, Galileo's camera (original image is inset in lower right corner). The bright lava curtain (a chain of lava fountains) and surface flows shown in the color image were assembled as an interpretive drawing by Galileo scientists, based on their knowledge of how the camera behaves when saturated. The lava appears to be producing fountains to heights of up to 1.5 kilometers (5,000 feet) above the surface. Several other lava flows can be seen on the floors of the calderas. The darkest flows are probably the most recent. The elongated caldera in the center of the image is almost surrounded by a mesa that is about 1 kilometer (.6 miles) high. In places the mesa's margins are scalloped, which is typical of an erosional process called sapping. This occurs when fluid escapes from the base of a cliff, causing the material above it to collapse. On Earth, sapping is caused by springs of groundwater. Similar features on Mars are one of the key pieces of evidence that water flowed on Mars' surface in the past. On Io, the fluid is believed to be sulfur dioxide, which should vaporize almost instantaneously when it reaches the near vacuum at Io's surface, blasting away material at the base of the cliffs. North is to the top of the image and the Sun illuminates the surface from the lower left. The high resolution black and white image was taken at a distance of 17,000 kilometers (11,000 miles). The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC. JPL is a division of the California Institute of Technology, Pasadena, CA. This image and other images and data received from Galileo are posted on the Galileo mission home page at http://galileo.jpl.nasa.gov . Background information and educational context for the images can be found at http://galileo.jpl.nasa.gov/images/io/ioimages.html . #####
Ongoing Volcanic Eruption at …
An active volcanic eruption …
5/31/00
Date 5/31/00
Description An 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). The Jet Propulsion Laboratory, Pasadena, Calif., manages the mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology in Pasadena. This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at http://galileo.jpl.nasa.gov . Background information and educational context for the images can be found at http://galileo.jpl.nasa.gov/images/io/ioimages.html . #####
An Ionian Caldera Up Close
Detail of one of the caldera …
5/31/00
Date 5/31/00
Description Detail of one of the calderas, or collapsed volcanic craters, on Jupiter's moon Io, is seen in these images acquired on February 22, 2000 by NASA's Galileo spacecraft. Taken from a distance of 700 to 800 kilometers (roughly 400 to 500 miles). The five partial images on the right comprise all of the data that could be returned from an eight-image mosaic. These are the highest resolution images of lava flows ever obtained from Io. The resolution of the close-up images varies from 7 to 8 meters (about 23 to 26 feet) per picture element. The boxes in the image to the left are approximate locations of the five partial images. They are shown superimposed on a lower resolution image of the entire Chaac caldera. The high-resolution snapshots highlight areas from both the southern and northern rims as well as areas on the floor of the caldera. They reveal fascinating similarities and differences between calderas on Io and Earth. Most puzzling is the texture of the material above the caldera rim. The plains surrounding Chaac are covered with alternating dark and light patches. The process that forms this surface is a complete mystery. By comparison, scientists analyzing the images say the floor of the caldera is amazingly familiar. The interwoven domes and pits form a surface essentially identical to many terrestrial calderas that erupt fluid lavas. For example, the similarity to the caldera on top of the Kilauea Volcano in Hawaii is striking. The southernmost Chaac image shows several raised plateaus and a deep, dark pit about 400 meters (about 440 yards) across. Although the Kilauea caldera is 10 times smaller than the Chaac caldera, the 1959 Kilauea eruption formed similar features to Chaac when a small volcanic crater was filled by erupting lava. The Hawaiian lava formed a pond that crusted over and then partially drained back down into the ground. Pieces of the pond crust that were left behind formed a perched plateau, and the hole the lava drained back into formed a deep pit. Scientists presume the same thing happened at Chaac in the recent past. The high-resolution images were taken at a distance of about 700- 800 kilometers (400-500 miles) and are centered around 12 degrees north latitude and 158 degrees west longitude. North is to the top and the sun illuminates the surface from the right. The lower resolution image was also taken on February 22, 2000 but from a distance of 18,800 kilometers (11,700 miles) from Io. The image is centered at 11.6 degrees north latitude and 157.7 degrees west longitude. North is to the top and the Sun illuminates the surface from the left. The Jet Propulsion Laboratory, Pasadena, Calif., manages the mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology, Pasadena, Calif. This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at http://galileo.jpl.nasa.gov . Background information and educational context for the images can be found at http://galileo.jpl.nasa.gov/images/io/ioimages.html . #####
Stereo Images of Tvashtar Ca …
This stereo image illustrate …
5/31/00
Date 5/31/00
Description This stereo image illustrates the topography of the Tvashtar Catena region on Jupiter's moon Io. It was created by combining two different views of Tvashtar taken by NASA's Galileo spacecraft on November 25, 1999 (shown in red) and February 22, 2000 (shown in blue). A raised plateau surrounds the volcanic depression, or caldera, in the center of the image. To the northeast of the main caldera, the plateau's inner and outer margins are scalloped, which may indicate that a process called sapping is eroding them. Sapping occurs when fluid escapes from the base of a cliff, causing the material above it to collapse. Smaller calderas have formed in the floor of the main caldera. This nesting of calderas is also observed on Earth, at Kilauea in Hawaii. (The two bright red regions toward the upper left of this image, which are roughly triangular in shape, are the areas where the earlier image was overexposed by the brightness of hot lava fountains). Galileo scientists are in the process of generating topographic maps from these images. Such maps will reveal the heights and slopes of different landforms in this region, which will help scientists determine the strength and other properties, of Io's surface materials. They will also be useful in understanding the processes of uplift and erosion on Io. The picture is centered at 59 degrees north latitude and 121 degrees west longitude. North is to the top of the picture and the Sun illuminates the surface from the lower left. The observations used to make the stereo image were made at ranges of 18,000 and 34,500 kilometers (11,400 and 21,600 miles) from Io. The resolution of the stereo image is about 320 meters (350 yards) per picture element. The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is a division of the California Institute of Technology, Pasadena, CA. This image and other images and data received from Galileo are posted on the Galileo mission home page at http://galileo.jpl.nasa.gov . Background information and educational context for the images can be found at http://galileo.jpl.nasa.gov/images/io/ioimages.html . #####
Stereo Image of Zal Patera a …
This stereo image of Jupiter …
5/31/00
Date 5/31/00
Description This stereo image of Jupiter's moon Io shows the topography of a region on Io that includes the Zal Patera feature and a mountain or plateau that borders it to the west. It was created by combining two different views taken by NASA's Galileo spacecraft on November 25, 1999 (shown in red) and February 22, 2000 (shown in blue). A mountain 120 kilometers (75 miles) wide rises to the west of the patera, a dark volcanic depression. By measuring the shadow, scientists were able to determine that the eastern margin of this mountain is about 1.5 kilometers (5000 feet) high. To the west and northwest, the mountain's margins are scalloped, which may indicate that a process called sapping is eroding them. Sapping occurs when fluid escapes from the base of a cliff, causing the material above it to collapse. Along the northwestern margin, the rough material at the base of the cliff may be debris left over from the sapping process. Dark lava flows can be seen coming from a fissure to the east of the mountain. Galileo scientists are in the process of generating topographic maps from these images. Such maps will reveal the heights and slopes of different landforms in this region, which will help scientists determine the strength and other properties of Io's surface materials. They will also be useful in understanding the processes of uplift and erosion on Io. The picture is centered at 42.3 degrees north latitude and 76.9 degrees west longitude. North is to the top of the picture. The observations used to make the stereo image were made at ranges of 26,000 and 33,500 kilometers (16,200 and 20,900 miles) from Io. The resolution of the stereo image is about 335 meters (370 yards) per picture element. The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC. JPL is a division of the California Institute of Technology, Pasadena, CA. This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at http://galileo.jpl.nasa.gov . Background information and educational context for the images can be found at http://galileo.jpl.nasa.gov/images/io/ioimages.htm . #####
Colorized View of Zal Region …
This image shows one of many …
5/31/00
Date 5/31/00
Description This image shows one of many intriguing mountains on Jupiter's moon Io. The image was made by combining a recent high- resolution, black and white image with earlier low-resolution color data to provide a high-resolution, color view. NASA's Galileo spacecraft took both images. The 240-kilometer (150-mile) long mountain in the image is south of the volcanic hot spot named Zal. The black and white version of this image was useful for showing the shape of the mountain and the small fans of debris piled against the base of its tall, steep cliffs. However, when colorized the relationship between different types of materials becomes apparent. For example, the bright, red material is believed to contain a compound of sulfur that forms when sulfur is boiled at a high temperature. Active eruptions of molten rock (lava) are the most likely source for the heat. Thus we see red sulfur where lava reaches the surface. Other sulfur compounds cover the yellow areas, and the black areas are fresh silicate lava that has not yet been coated by the yellow sulfurous materials. The green patches are still somewhat mysterious, they appear to form when red sulfur lands on warm lava and the two react in a manner that is still unknown. In this image, it is clear that the red material has blown out of a long crack along the western side of the mountain. Lava has flowed from this crack and filled a depression (caldera). Some of the red sulfur close to the dark caldera appears to have been converted into green material. The fact that lava comes up along the faults that define the sides of the mountains provides important clues to how the mountains form and the state of the interior of Io. Scientists at the University of Arizona speculate that the formation of the mountains on Io may be related to plumes of hot material rising inside the fiery body of Io. North is to the top and the setting sun is shining from the west. The image is centered at about 33 degrees north, 72 degrees west. The high-resolution image was taken on February 22, 2000 by NASA's Galileo spacecraft. The image was taken by the Galileo's onboard camera from a range of 33,500 kilometers (20,800 miles) and has a resolution of 335 meters (1,100 feet) per picture element. The color images were taken on July 3, 1999. They have resolutions of 1.3 kilometers (0.81 miles) per picture element and are illuminated from almost directly behind the spacecraft. They were taken at a distance of about 130,000 kilometers (81,000 miles) from Io. The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC. JPL is a division of the California Institute of Technology, Pasadena, CA. This image and other images and data received from Galileo are posted on the Galileo mission home page at http://galileo.jpl.nasa.gov . Background information and educational context for the images can be found at http://galileo.jpl.nasa.gov/images/io/ioimages.html. #####
Shamshu Mons and Patera, Io
This mosaic of images taken …
5/31/00
Date 5/31/00
Description This mosaic of images taken by NASA's Galileo spacecraft on February 22, 2000 shows three mountains and two lava-filled depressions in the Shamshu region of Jupiter's moon Io. The dark oval feature on the left side of the image is a depression that has been resurfaced by lava flows. The rough terrain northeast of the depression is Shamshu Mons. A 10-kilometer (6-mile) wide canyon oriented in northeast to southwest direction cuts this mountain. The northwestern edge of the mountain has been scalloped by erosion, and it appears that the material has flowed along the canyon floor. Portions of two more mountains can be seen on the right side of the image. The depression between these mountains is Shamshu Patera, a volcanic hotspot. The dark patches within it are recent and active lava flows. The northernmost edge of Shamshu Patera appears to be cutting into the mountain to its northeast. North is to the top of the picture and the Sun illuminates the surface from the west. This mosaic has a resolution of about 345 meters (1,130 feet) per picture element and covers an area approximately 390 by 380 kilometers (240 by 235 miles) at its maximum dimensions. It is centered at about 9 degrees south latitude and 68 degrees west longitude. The images that make up this mosaic were acquired at a range of 34,500 kilometers (21,400 miles) by Galileo's onboard camera. The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC. JPL is a division of the California Institute of Technology, Pasadena, CA. This image and other images and data received from Galileo are posted on the Galileo mission home page at http://galileo.jpl.nasa.gov . Background information and educational context for the images can be found at http://galileo.jpl.nasa.gov/images/io/ioimages.html . #####
Lava Flows and Ridged Plains …
The margin of the lava flow …
5/31/00
Date 5/31/00
Description The margin of the lava flow field associated with the Prometheus volcanic plume on Jupiter's moon Io is seen in this image, acquired by NASA's Galileo spacecraft on February 22, 2000. The image has a resolution of 12 meters (39 feet) per picture element. The dark lava has margins similar to those formed by fluid lava flows on Earth. This entire area is under the active plume of Prometheus, which is constantly raining bright material. Hence, Galileo scientists interpret the darkest flows as being the most recent. They are not yet covered by bright plume fallout and perhaps too warm for bright gas rich in sulphur dioxide to condense. The older plains (upper right) are covered by ridges with an east-west trend. These ridges may have formed by the folding of a surface layer or by deposition or erosion. Bright streaks across the ridged plains emanate from the lava flow margins, perhaps where the hot lava vaporizes sulphur dioxide. The bright material must be ejected at a low angle because it only coats the lava-facing sides of the ridges. North is slightly to the right of straight up. The Jet Propulsion Laboratory, Pasadena, Calif., manages the mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology, Pasadena, Calif. This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at http://galileo.jpl.nasa.gov . Background information and educational context for the images can be found at http://galileo.jpl.nasa.gov/images/io/ioimages.html .
Ganymede dark terrain at hig …
Impact craters dominate the …
12/16/00
Date 12/16/00
Description Impact craters dominate the surface down to the smallest features visible on the dark terrain of the Nicholson Regio region of Jupiter's moon Ganymede in this image taken by NASA's Galileo spacecraft. It is the highest resolution view ever obtained of Ganymede's dark terrain. Both the regional-scale image at the bottom and high- resolution image at the top were taken by Galileo during its May 20, 2000, flyby of Ganymede. The latter are the highest resolution images ever obtained of Ganymede's dark terrain, which makes up about one third of Ganymede's surface. Impact cratering is clearly the dominant mechanism of surface modification in this relatively ancient terrain, which is analogous to the cratered highlands of Earth's Moon. Small- scale craters seem to mimic larger-scale craters, as is apparent in the similarities between the high and medium resolution scenes. The bright spots are probably fresh ice-rich ejecta excavated by the most recent impact events. North is to the top of the images and the Sun illuminates the surface from the west. The medium-resolution image, centered at –15 degrees latitude and 337 degrees longitude, covers an area approximately 237 by 130 kilometers (147 by 81 miles) at a resolution of 125 meters (410 feet) per picture element. The high-resolution image is at 28 meters (92 feet) per picture element. This image and other images and data received from Galileo are posted on the Galileo mission home page at http://www.jpl.nasa.gov/galileo . Background information and educational context for the images can be found at http://www.jpl.nasa.gov/galileo/sepo . The Jet Propulsion Laboratory, a division of the California Institute of Technology, in Pasadena, manages the Galileo mission for NASA's Office of Space Science, Washington, D.C. The images were produced by Arizona State University, Tempe, and Brown University, Providence, R.I.. Their websites are at http://europa.la.asu.edu/index.html and http://www.planetary.brown.edu/ . # # # # #
Region of Ganymede with mix …
The area of Nicholson Regio …
12/16/00
Date 12/16/00
Description The area of Nicholson Regio and Arbela Sulcus illustrates many of the diverse terrain types on Jupiter's moon Ganymede, as seen in this image taken by NASA's Galileo spacecraft. The bright terrain of Arbela Sulcus is the youngest terrain here, slicing north-south across the image. It is finely striated, and relatively lightly cratered. To the east (right) is the oldest terrain in this area, rolling and relatively densely cratered Nicholson Regio. To the west (left) is a region of highly deformed grooved terrain, intermediate in relative age. In this area of grooved terrain, stretching and normal faulting of Nicholson Regio has deformed it beyond recognition. North is to the top of the picture and the Sun illuminates the surface from the west. The image, centered at -15 degrees latitude and 347 degrees longitude, covers an area approximately 89 by 26 kilometers (55 by 16 miles). The resolution is 34 meters (112 feet) per picture element. The images were taken on May 20, 2000, at a range of 3,350 kilometers (2,082 miles). This image and other images and data received from Galileo are posted on the Galileo mission home page at http://www.jpl.nasa.gov/galileo . Background information and educational context for the images can be found at http://www.jpl.nasa.gov/galileo/sepo . The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Galileo mission for NASA's Office of Space Science, Washington, D.C. This image was produced by DLR (German Aerospace Center), Berlin, and Brown University, Providence, R.I., http://solarsystem.dlr.de/ and http://www.planetary.brown.edu/ . # # # # #
Regional view of bright and …
This view of the Nicholson R …
12/16/00
Date 12/16/00
Description This view of the Nicholson Regio/Arbela Sulcus region on Jupiter's moon Ganymede, taken by NASA's Galileo spacecraft, shows the stark contrast between the smooth bright terrain and the surrounding highly fractured dark terrain. This observation was designed in part to distinguish between different models for how Arbela Sulcus and other groove lanes on Ganymede were formed. The volcanic model suggests that a relatively clean, water-rich lava filled a tectonic depression, then cooled to create a smooth surface. Tectonic models suggest that focused faulting and deformation of older dark terrain destroyed the pre-existing texture, which was brightened by exposure of underlying, clean ice. Analysis of these photos suggests a third and unexpected possibility: Arbela Sulcus may be similar to some bands on another of Jupiter's moons, Europa, formed by tectonic crustal spreading and renewal. North is to the upper left of the picture and the Sun illuminates the surface from the west. The image, centered at – 14 degrees latitude and 347 degrees longitude, covers an area approximately 258 by 116 kilometers (160 by 72 miles). The resolution is 133 meters (436 feet) per picture element. The images were taken on May 20, 2000, at a range of 13,100 kilometers (8,140 miles). This image and other images and data received from Galileo are posted on the Galileo mission home page at http://www.jpl.nasa.gov/galileo . Background information and educational context for the images can be found at http://www.jpl.nasa.gov/galileo/sepo . The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Galileo mission for NASA's Office of Space Science, Washington, D.C. This image was produced by DLR (German Aerospace Center), Berlin, and Brown University, Providence, R.I., http://solarsystem.dlr.de/ and http://www.planetary.brown.edu/ . # # # # #
Ganymede feature resembling …
This frame compares a high-r …
12/16/00
Date 12/16/00
Description This frame compares a high-resolution view of Arbela Sulcus on Jupiter's moon 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 -15 degrees 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). This image and other images and data received from Galileo are posted on the Galileo mission home page at http://www.jpl.nasa.gov/galileo . Background information and educational context for the images can be found at http://www.jpl.nasa.gov/galileo/sepo . The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Galileo mission for NASA's Office of Space Science, Washington, D.C. This image was produced by DLR (German Aerospace Center), Berlin, and Brown University, Providence, R.I., http://solarsystem.dlr.de/ and http://www.planetary.brown.edu/ . # # # # #
Comparison of Ganymede and E …
This image, taken by NASA's …
12/16/00
Date 12/16/00
Description This image, taken by NASA's Galileo spacecraft, shows a same-scale comparison between Arbela Sulcus on Jupiter's moon Ganymede (left) and an unnamed band on another Jovian moon, Europa (right). Arbela Sulcus is one of the smoothest lanes of bright terrain identified on Ganymede, and shows very subtle striations along its length. Arbela contrasts markedly from the surrounding heavily cratered dark terrain. On Europa, dark bands have formed by tectonic crustal spreading and renewal. Bands have sliced through and completely separated pre-existing features in the surrounding bright ridged plains. The scarcity of craters on Europa illustrates 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. Prominent fractures on either side of Arbela appear to have been offset by about 65 kilometers (about 40 miles) along the length of the area of furrows and ridges, suggesting that strike-slip faulting was important in the formation of Arbela Sulcus. In the Ganymede image, north is to the upper left of the picture and the Sun illuminates the surface from the west. The image, centered at -14 degrees latitude and 347 degrees longitude, covers an area approximately 258 by 116 kilometers (160 by 72 miles.) The resolution is 133 meters (436 feet) per picture element. The images were taken on May 20, 2000, at a range of 13,100 kilometers (8,100 miles). In the Europa image, north is to the left of the picture and the Sun illuminates the surface from the east. The image, centered at -7 degrees latitude and 236 degrees longitude, covers an area approximately 275 by 424 kilometers (171 by 263 miles.) The resolution is 220 meters (about 720 feet) per picture element (re-sampled here to 133 meters, or 436 feet). The images were taken on Nov. 6, 1997, at a range of 21,500 kilometers (13,360 miles). The Jet Propulsion Laboratory, Pasadena, Calif., manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is a division of the California Institute of Technology in Pasadena. Images and data received from Galileo are posted on the Galileo mission home page at http://www.jpl.nasa.gov/galileo. Background information and educational context for the images can be found at http://www.jpl.nasa.gov/galileo/sepo . Images were produced by Brown University, Providence, R.I., http://www.planetary.brown.edu/, DLR (German Aerospace Center) Berlin, http://solarsystem.dlr.de , and University of Arizona, Tempe, http://www.lpl.arizona.edu/. # # # # #
Perspective view of Arbela S …
This view of Arbela Sulcus, …
12/16/00
Date 12/16/00
Description This view of Arbela Sulcus, a 24-kilometer-wide (15-mile- wide) region of furrows and ridges on Jupiter's moon Ganymede, shows its relationship to the dark terrain surrounding it. NASA's Galileo spacecraft took these pictures during its May 20, 2000, flyby of Ganymede. Arbela Sulcus lies overall slightly lower than the dark terrain of Nicholson Regio, a 3,700 kilometers (3,300 mile) area in the southern hemisphere. However, along the eastern margin (bottom), a portion of the dark terrain (probably an ancient degraded impact crater) lies even lower than Arbela Sulcus. Scientists did not find bright icy material on Arbela Sulcus, indicating that this ridgy area was not created by watery volcanic activity. Instead, they found fine striations covering the surface, along with a series of broader highs and lows that resemble piano keys. This suggests that the movement of underlying tectonic plates deformed the surface. Combining images from two observations taken from different viewing perspectives provides stereo topographic information, giving valuable clues as to the geologic history of a region. North is to the right of the image. The Sun illuminates the surface from the west. The image, centered at –15 degrees latitude and 347 degrees longitude, covers an area approximately 89 by 26 kilometers (55 by 16 miles). The image resolution is 70 meters (230 feet) per picture element. The images were taken on May 20, 2000, at a range of 3,350 kilometers (2,100 miles). The Jet Propulsion Laboratory, Pasadena, Calif., manages the Galileo mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology in Pasadena. This image and other images and data received from Galileo are posted on the Galileo mission home page at http://www.jpl.nasa.gov/galileo . The images were produced by German Aerospace Center (DLR), http://solarsystem.dlr.de/ Background information and educational context for the images can be found at http://www.jpl.nasa.gov/galileo/sepo . # # # # #
Bright-Dark terrain boundary …
The boundary between the bri …
12/16/00
Date 12/16/00
Description The boundary between the bright terrain of Harpagia Sulcus (right) and dark terrain of Nicholson Regio (left) areas of Jupiter's moon Ganymede springs out when viewed through red/blue 3-D glasses, in this image taken by NASA's Galileo spacecraft as it flew by Ganymede on May 20, 2000. Details of the rough, ancient, heavily cratered dark terrain of Nicholson Regio are in stark contrast to the very smooth, bright, young terrain of Harpagia Sulcus. In the center lies the transition to the boundary between these two regions, providing evidence that extensional faulting marks the boundary. A series of steep slopes deform the dark terrain close to the boundary. In the bright terrain, a deep trough and flanking ridge delimit the boundary. North is to the top of the picture. The Sun illuminates the surface from the left. The imaged region, centered at –14 degrees latitude and 319 degrees longitude, covers an area approximately 25 by 10 kilometers (15.5 by 6 miles.) The resolutions of the two data sets are 20 meters (66 feet) per picture element and 121 meters (397 feet) per picture element. The higher resolution images were taken at a range of 2,000 kilometers (about 1,200 miles). The Jet Propulsion Laboratory, Pasadena, Calif., manages the Galileo mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology in Pasadena. This image and other images and data received from Galileo are posted on the Galileo mission home page at http://www.jpl.nasa.gov/galileo . The image was produced by the German Aerospace Center (DLR), http://solarsystem.dlr.de and Brown University, http://www.planetary.brown.edu/ . Background information and educational context for the images can be found at http://www.jpl.nasa.gov/galileo/sepo . # # # # #
Bright-dark boundary and top …
These images, taken by NASA' …
12/16/00
Date 12/16/00
Description These images, taken by NASA's Galileo spacecraft on its May 20, 2000, flyby of Jupiter's moon Ganymede, illustrate the boundary and different elevations between the dark, ancient terrain of Nicholson Regio (left) and bright, younger terrain of Harpagia Sulcus (right.) The bottom image is a wide view of the boundary, and the top image is an enlargement of the colorized strip. An important goal of Galileo's Ganymede encounter was to understand the nature of the boundary between ancient, dark terrain and younger, bright terrain. The camera was aimed at the boundary to obtain both very high-resolution images (top) and medium-resolution context images (bottom). Color-coded elevations are indicated relative to the average elevation of the sampled area, with high elevation marked in red, and low in blue. Combining the two image mosaics allows scientists to derive a detailed description of the region from the overlap. The data shows that there are approximately 200 meters (about 650 feet) of topographic relief within the bright terrain here, and a deep depression marks the boundary between bright and dark terrains. North is to the top of the pictures. The Sun illuminates the surface from the left. The larger image, centered at –14 degrees latitude and 319 degrees longitude, covers an area approximately 213 by 97 kilometers (132 by 60 miles.) The resolution of the high-resolution image is 20 meters (about 65 feet) per picture element, and the context image is at 121 meters (397 feet) per picture element. The higher resolution image was taken at a range of 2000 kilometers (over 1,200 miles). The Jet Propulsion Laboratory, Pasadena, Calif., manages the Galileo mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology in Pasadena. This image and other images and data received from Galileo are posted on the Galileo mission home page at http://www.jpl.nasa.gov/galileo . The images were produced by the German Aerospace Center (DLR) http://solarsystem.dlr.de/ , and Brown University, http://www.planetary.brown.edu/ . Background information and educational context for the images can be found at http://www.jpl.nasa.gov/galileo/sepo . # # # # #
Caldera-like depression on G …
The shallow, scalloped depre …
12/16/00
Date 12/16/00
Description The shallow, scalloped depression in the center of this picture from NASA's Galileo spacecraft is a caldera-like feature 5 to 20 kilometers (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 and available at http://photojournal.jpl.nasa.gov/cgi- bin/PIAGenCatalogPage.pl?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 318 degrees longitude, covers an area approximately 162 by 119 kilometers (101 by 74 miles). The resolution is 43 meters (141 feet) per picture element. This image and other images and data received from Galileo are posted on the Galileo mission home page at http://www.jpl.nasa.gov/galileo . Background information and educational context for the images can be found at http://www.jpl.nasa.gov/galileo/sepo . The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Galileo mission for NASA's Office of Space Science, Washington, D.C. This image was produced by Brown University, Providence, R.I., http://www.planetary.brown.edu/ . # # # # #
Not-so-smooth bright terrain …
The highest-resolution image …
12/16/00
Date 12/16/00
Description The highest-resolution images ever obtained of Jupiter's moon Ganymede show that even smooth-looking terrain has been deformed at a fine scale. The high-resolution image taken of the bright Harpagia Sulcus area by NASA's Galileo spacecraft during a May 20, 2000, flyby of Ganymede shows features as small as 16 meters (52 feet). This area was selected for a closer look because, in images taken by NASA's Voyager spacecraft about 20 years earlier, it looked as flat as a hockey rink. It appears smooth even in a medium-resolution Galileo image (at 116 meters or 380 feet per pixel) that is superimposed over a Voyager image in the top portion of this frame. But the closeup shot revealed that, instead of a hockey rink, the area has ups and downs that would be challenging for a cross-country skier. North is to the top of the picture and the Sun illuminates the surface from the left. The medium-resolution image mosaic is centered at -16 degrees latitude and 310 degrees longitude, and covers an area approximately 282 by 144 kilometers (175 by 89 miles). This image and other images and data received from Galileo are posted on the Galileo mission home page at http://www.jpl.nasa.gov/galileo . Background information and educational context for the images can be found at http://www.jpl.nasa.gov/galileo/sepo . The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Galileo mission for NASA's Office of Space Science, Washington, D.C. This image was produced by DLR (German Aerospace Center), Berlin, and Brown University, Providence, R.I., http://solarsystem.dlr.de/ and http://www.planetary.brown.edu/ . # # # # #
Stair-step scarps in dark te …
NASA's Galileo spacecraft to …
12/16/00
Date 12/16/00
Description 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 degrees latitude and 320 degrees longitude, and covers an area approximately 16 by 15 kilometers (10 by 9 miles). The resolution is 20 meters (66 feet) per picture element. The image was taken on May 20, 2000, at a range of 2,090 kilometers (1,299 miles). This image and other images and data received from Galileo are posted on the Galileo mission home page at http://www.jpl.nasa.gov/galileo . Background information and educational context for the images can be found at http://www.jpl.nasa.gov/galileo/sepo . The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Galileo mission for NASA's Office of Space Science, Washington, D.C. This image was produced by Brown University, Providence, R.I., http://www.planetary.brown.edu/ . # # # # #
Eruption at Tvashtar Catena …
This pair of images taken by …
2/26/01
Date 2/26/01
Description This pair of images taken by NASA's Galileo spacecraft captures a dynamic eruption at Tvashtar Catena, a chain of volcanic bowls on Jupiter's moon Io. They show a change in the location of hot lava over a period of a few months in 1999 and early 2000. The image on the left uses data obtained on Nov. 26 and July 3, 1999, at resolutions of 183 meters (600 feet) and 1.3 kilometers (0.8 miles) per pixel, respectively. The red and yellow lava flow itself is an illustration based upon imaging data. The image on the right is a composite using a five-color observation made on Feb. 22, 2000, at 315 meters (1030 feet) per pixel. These are among the most fortuitous observations made by Galileo because this style of volcanism is too unpredictable and short-lived to plan to photograph. Short-lived bursts of volcanic activity on Io had been previously detected from Earth-based observations, but interpreting the style of volcanic activity from those lower- resolution views was highly speculative. These Galileo observations confirm hypotheses that the initial, intense thermal output comes from active lava fountains. Galileo's high-resolution observations of volcanic activity on Io have also confirmed other hypotheses based on earlier, low- resolution data. These include interpretations of slowly spreading lava flows at Prometheus and Amirani and an active lava lake at Pele. These tests of earlier hypotheses increase scientists' confidence in interpreting volcanic activity seen in low-resolution remote sensing data of Earth as well as Io. However, these data are still of insufficient resolution to adequately test the more quantitative models that have been applied to volcanic eruptions on Earth and Io. These images also show other geologic features on Io, such as the scalloped margins of the plateau to the northeast of the active lavas. These margins appear to have formed by sapping, a process usually associated with springs of water. Liquid sulfur dioxide might be the fluid responsible for sapping on Io. A better understanding of sapping on Io will influence how scientists interpret similar features on Mars (where the viability of carbon dioxide or water as the sapping fluid remains controversial). Images and data received from Galileo are posted on the Galileo mission home page at http://www.jpl.nasa.gov/galileo. Background information and educational context for the images can be found at http://www.jpl.nasa.gov/galileo/sepo . The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Galileo mission for NASA's Office of Space Science, Washington, D.C. # # # # #
Amirani's Big Lava Flow on I …
These images from NASA's Gal …
2/26/01
Date 2/26/01
Description These images from NASA's Galileo spacecraft show changes in the largest active field lava flows in the solar system, the Amirani lava flow on Jupiter's moon Io. Scientists have identified 23 distinct new flows by comparing the two images taken 134 days apart, on Oct. 11, 1999, and Feb. 22, 2000. The Amirani lava-flow field spans more than 300 kilometers (190 miles). Individual flows within it are each several kilometers or miles long, which is about the size of the entire active eruption on Kilauea, Hawaii. In total, the new lava flows at Amirani covered about 620 square kilometers (240 square miles) of Io in less than five months. By comparison, Kilauea covered only about 10 square kilometers (4 square miles) in the same time. Amirani is huge even when compared to other Ionian lava flows: The Prometheus lava flow field covered only about 60 square kilometers (24 square miles) during this time. Galileo scientists are studying Amirani to understand how such large lava flows are created. The last eruption this size on Earth happened about 15 million years ago along the Columbia River in what is now the state of Washington. Many scientists thought that such long lava flows were formed in violent volcanic outbursts. However, the eruption observed at Amirani is relatively calm, despite the fact that over 100 tons of lava are disgorged every second. Galileo's observations of Io indicate that huge, ancient lava flows on the Earth, such as the Columbia River flood basalts, could also have formed in relatively tranquil eruptions. The color image on the left is a composite of black-and- white images collected on Feb. 22, 2000, at a resolution of 210 meters (690 feet) per picture element, and color images collected on June 30, 1999, at 1.3 kilometers (0.8 mile) per picture element. The white boxes and arrows show the locations of the areas analyzed in detail on the right. The left-hand pair of black-and-white images, labeled I24, are parts of a mosaic collected on Oct. 11, 1999, at 500 meters (550 yards) per picture element. The center pair of images, labeled I27, shows what the same areas looked like on Feb. 22, 2000. These later images are about twice as sharp as the earlier images, making some features that did not change appear crisper. In order to demonstrate the real changes, the I27 images were divided by the I24 images, producing the pair of ratio images on the right. The new dark lava that erupted between October 1999 and February 2000 has been highlighted in red. Images and data received from Galileo are posted on the Galileo mission home page at http://www.jpl.nasa.gov/galileo. Background information and educational context for the images can be found at http://www.jpl.nasa.gov/galileo/sepo . The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Galileo mission for NASA's Office of Space Science, Washington, D.C. # # # # #
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