Galerie de photos de Io, satellite galiléen de la planète Jupiter

<h1>PIA02547: The Role of Sulfur in Io's Volcanoes</h1><div class="PIA02547" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>Current scientific ideas about the role of sulfur in volcanoes on Jupiter's moon Io are illustrated. Sulfur gas consisting of pairs of sulfur atoms (S2), detected above Io's volcano Pele by the Hubble Space Telescope in October 1999, is ejected from the hot vents of Io's volcanoes (green arrow). The sulfur gas lands on the cold surface, where the sulfur atoms rearrange into molecules of three or four atoms (S3, S4), which give the surface a red color. Eventually the atoms rearrange into their most stable configuration, rings of eight atoms (S8), which form ordinary pale yellow sulfur.</p><p>Additional information about the Hubble Space Telescope is available at<a href="http://www.stsci.edu/hst/" class="external free" target="wpext">http://www.stsci.edu/hst/</a>. Additional information about the Galileo mission is available at <a href="http://galileo.jpl.nasa.gov" class="external free" target="wpext">http://galileo.jpl.nasa.gov</a>.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02547" onclick="window.open(this.href); return false;" title="Voir l'image PIA02547: The Role of Sulfur in Io's Volcanoes sur le site de la NASA">Voir l'image PIA02547: The Role of Sulfur in Io's Volcanoes sur le site de la NASA.</a></div>
PIA02547: The Role of Sulfur in Io's Volcanoes
<h1>PIA02550: Ongoing Volcanic Eruption at Tvashtar Catena, Io</h1><div class="PIA02550" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>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.</p><p>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).</p><p>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.</p><p>This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at <a href="http://solarsystem.nasa.gov/galileo/" target="_blank">http://solarsystem.nasa.gov/galileo/</a>. Background information and educational context for the images can be found at <a href="http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jup_Io" target="_blank">http://galileo.jpl.nasa.gov/gallery/io.cfm</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02550" onclick="window.open(this.href); return false;" title="Voir l'image PIA02550: Ongoing Volcanic Eruption at Tvashtar Catena, Io sur le site de la NASA">Voir l'image PIA02550: Ongoing Volcanic Eruption at Tvashtar Catena, Io sur le site de la NASA.</a></div>
PIA02550: Ongoing Volcanic Eruption at Tvashtar Catena, Io
<h1>PIA02551: Snapshots of Chaac: Io's calderas up close</h1><div class="PIA02551" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>Detail of one of the calderas, or collapsed volcanic craters, on Jupiter's moon Io, is seen in these images acquired on February 22, 2000by 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.</p><p>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.</p><a href="/figures/grand_cyn.jpg"></a><p>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.</p><p>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.</p><p>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.</p><p>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.</p><p>This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at <a href="http://solarsystem.nasa.gov/galileo/" class="external free" target="wpext">http://solarsystem.nasa.gov/galileo/</a>. Background information and educational context for the images can be found at <a href="http://solarsystem.nasa.gov/galileo/gallery/index.cfm" class="external free" target="wpext">http://solarsystem.nasa.gov/galileo/gallery/index.cfm</a>.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02551" onclick="window.open(this.href); return false;" title="Voir l'image PIA02551: Snapshots of Chaac: Io's calderas up close sur le site de la NASA">Voir l'image PIA02551: Snapshots of Chaac: Io's calderas up close sur le site de la NASA.</a></div>
PIA02551: Snapshots of Chaac: Io's calderas up close
<h1>PIA02552: Stereo Image of Tvashtar Catena, Io</h1><div class="PIA02552" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>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).</p><p>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).</p><p>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.</p><p>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.</p><p>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.</p><p>This image and other images and data received from Galileo are posted on the Galileo mission home page at <a href="http://solarsystem.nasa.gov/galileo/" target="_blank">http://solarsystem.nasa.gov/galileo/</a>. Background information and educational context for the images can be found at <a href="http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jup_Io" target="_blank">http://galileo.jpl.nasa.gov/gallery/io.cfm</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02552" onclick="window.open(this.href); return false;" title="Voir l'image PIA02552: Stereo Image of Tvashtar Catena, Io sur le site de la NASA">Voir l'image PIA02552: Stereo Image of Tvashtar Catena, Io sur le site de la NASA.</a></div>
PIA02552: Stereo Image of Tvashtar Catena, Io
<h1>PIA02553: Stereo Image of Zal Patera and Neighboring Mountain, Io</h1><div class="PIA02553" lang="en" style="width:506px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>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).</p><p>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 maybe debris left over from the sapping process. Dark lava flows can be seen coming from a fissure to the east of the mountain.</p><p>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.</p><p>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.</p><p>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.</p><p>This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at <a href="http://solarsystem.nasa.gov/galileo/" class="external free" target="wpext">http://solarsystem.nasa.gov/galileo/</a>. Background information and educational context for the images can be found at <a href="http://solarsystem.nasa.gov/galileo/gallery/index.cfm" class="external free" target="wpext">http://solarsystem.nasa.gov/galileo/gallery/index.cfm</a>.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02553" onclick="window.open(this.href); return false;" title="Voir l'image PIA02553: Stereo Image of Zal Patera and Neighboring Mountain, Io sur le site de la NASA">Voir l'image PIA02553: Stereo Image of Zal Patera and Neighboring Mountain, Io sur le site de la NASA.</a></div>
PIA02553: Stereo Image of Zal Patera and Neighboring Mountain, Io
<h1>PIA02554: Colorized View of Zal Region, Io</h1><div class="PIA02554" lang="en" style="width:643px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>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.</p><p>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.</p><p>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.</p><p>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.</p><p>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.</p><p>This image and other images and data received from Galileo are posted on the Galileo mission home page at <a href="http://solarsystem.nasa.gov/galileo/" target="_blank">http://solarsystem.nasa.gov/galileo/</a>. Background information and educational context for the images can be found at <a href="http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jup_Io" target="_blank">http://galileo.jpl.nasa.gov/gallery/io.cfm</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02554" onclick="window.open(this.href); return false;" title="Voir l'image PIA02554: Colorized View of Zal Region, Io sur le site de la NASA">Voir l'image PIA02554: Colorized View of Zal Region, Io sur le site de la NASA.</a></div>
PIA02554: Colorized View of Zal Region, Io
<h1>PIA02555: Shamshu Mons and Patera, Io</h1><div class="PIA02555" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>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. A10-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.</p><p>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.</p><p>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.</p><p>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.</p><p>This image and other images and data received from Galileo are posted on the Galileo mission home page at <a href="http://solarsystem.nasa.gov/galileo/" target="_blank">http://solarsystem.nasa.gov/galileo/</a>. Background information and educational context for the images can be found at <a href="http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jup_Io" target="_blank">http://galileo.jpl.nasa.gov/gallery/io.cfm</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02555" onclick="window.open(this.href); return false;" title="Voir l'image PIA02555: Shamshu Mons and Patera, Io sur le site de la NASA">Voir l'image PIA02555: Shamshu Mons and Patera, Io sur le site de la NASA.</a></div>
PIA02555: Shamshu Mons and Patera, Io
<h1>PIA02556: Highest-Resolution Picture of Io</h1><div class="PIA02556" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>This image, acquired by NASA's Galileo spacecraft on February 22, 2000, is the highest resolution image ever taken of Io. The resolution is 5.2 meters (18 feet) per picture element.<p>Galileo viewed the surface obliquely, tilted 72 degrees from straight overhead. Illumination is from the lower right, but the topographic shading is difficult to see because of the strong contrasts in brightness of the surface materials. The bright areas are generally higher in elevation than adjacent dark areas. The surface appears to have been eroded by an unknown process, in places exposing layers of bright and dark material. Evaporation of solid ice may also play a role in separating the bright and dark materials. North is toward the upper right.<p>Also shown is a version of this image processed to give a bird's-eye view over the terrain. This image maps out the true distribution of bright and dark surface materials.<p><a href="/figures/saporth.jpg"></a><p>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.<p>This image and other images and data received from Galileo are posted on the Galileo mission home page at <a href="http://solarsystem.nasa.gov/galileo/" target="_blank">http://solarsystem.nasa.gov/galileo/</a>. Background information and educational context for the images can be found at <a href="http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jup_Io" target="_blank">http://galileo.jpl.nasa.gov/gallery/io.cfm</a>.<p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02556" onclick="window.open(this.href); return false;" title="Voir l'image PIA02556: Highest-Resolution Picture of Io sur le site de la NASA">Voir l'image PIA02556: Highest-Resolution Picture of Io sur le site de la NASA.</a></div>
PIA02556: Highest-Resolution Picture of Io
<h1>PIA02557: Lava Flows and Ridged Plains at Prometheus, Io</h1><div class="PIA02557" lang="en" style="width:618px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>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.</p><p>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.</p><p>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.</p><p>This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at <a href="http://solarsystem.nasa.gov/galileo/" class="external free" target="wpext">http://solarsystem.nasa.gov/galileo/</a>. Background information and educational context for the images can be found at <a href="http://solarsystem.nasa.gov/galileo/gallery/index.cfm" class="external free" target="wpext">http://solarsystem.nasa.gov/galileo/gallery/index.cfm</a>.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02557" onclick="window.open(this.href); return false;" title="Voir l'image PIA02557: Lava Flows and Ridged Plains at Prometheus, Io sur le site de la NASA">Voir l'image PIA02557: Lava Flows and Ridged Plains at Prometheus, Io sur le site de la NASA.</a></div>
PIA02557: Lava Flows and Ridged Plains at Prometheus, Io
<h1>PIA02558: Myriad of Hot Spots on Io</h1><div class="PIA02558" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>Changes in the volcanoes on Jupiter's moon Io can be seen in these three views, taken by NASA's Galileo spacecraft during its three flybys of Io in October 1999, November 1999 and February 2000.</p><p>All the images show the active volcanoes as bright yellow, corresponding to hot lava flows that appear glowing in infrared wavelengths. The three views were taken by the spacecraft's near-infrared mapping spectrometer instrument and show the comparison of a typical low-resolution observation to the high-resolution views. The regional observations taken during the recent Io flybys are superimposed on an image taken during Galileo in 1996.</p><p>The Prometheus volcano is seen near the middle of all three images. Before the recent flybys, only Prometheus and three other volcanoes were known to be active in this region. After these and other high-resolution observations, scientists were able to detect 14 volcanoes in the same area. The fainter volcanoes (hot spots) show some significant changes over intervals of 1 to 3 months. The area shown by all three observations put together is about 2 million square kilometers (about 770,000 square miles) and covers about 5 percent of Io's surface.</p><p>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.</p><p>This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at <a href="http://solarsystem.nasa.gov/galileo/" class="external free" target="wpext">http://solarsystem.nasa.gov/galileo/</a>. Background information and educational context for the images can be found at <a href="http://solarsystem.nasa.gov/galileo/gallery/index.cfm" class="external free" target="wpext">http://solarsystem.nasa.gov/galileo/gallery/index.cfm</a>.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02558" onclick="window.open(this.href); return false;" title="Voir l'image PIA02558: Myriad of Hot Spots on Io sur le site de la NASA">Voir l'image PIA02558: Myriad of Hot Spots on Io sur le site de la NASA.</a></div>
PIA02558: Myriad of Hot Spots on Io
<h1>PIA02559: Sulphur Dioxide on the Chaac Region of Io</h1><div class="PIA02559" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>This image shows the Chaac region, on Jupiter's moon Io, viewed by two instruments on NASA's spacecraft Galileo during the flyby on February 22, 2000. On the left is an image taken by Galileo's onboard camera. On the right is a map of the relative abundance of sulphur dioxide obtained from an observation made by the infrared spectrometer, an instrument onboard Galileo. The right map shows that the bright white material inside the small caldera just to the east of Chaac (lower right in the camera image) is filled by sulphur dioxide. This sulphur dioxide is purer than at any other location so far observed on Io. It may represent a frozen layer of sulphur dioxide ice on the floor of the caldera. The width of the image seen on the right map is about 100 kilometers (62 miles).</p><p>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.</p><p>This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at <a href="http://solarsystem.nasa.gov/galileo/" class="external free" target="wpext">http://solarsystem.nasa.gov/galileo/</a>. Background information and educational context for the images can be found at <a href="http://solarsystem.nasa.gov/galileo/gallery/index.cfm" class="external free" target="wpext">http://solarsystem.nasa.gov/galileo/gallery/index.cfm</a>.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02559" onclick="window.open(this.href); return false;" title="Voir l'image PIA02559: Sulphur Dioxide on the Chaac Region of Io sur le site de la NASA">Voir l'image PIA02559: Sulphur Dioxide on the Chaac Region of Io sur le site de la NASA.</a></div>
PIA02559: Sulphur Dioxide on the Chaac Region of Io
<h1>PIA02562: Very High Resolution View of Io's Surface</h1><div class="PIA02562" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>This mosaic of images acquired by NASA's Galileo spacecraft on February 22,2000, shows the highest resolution view ever obtained of the surface of Jupiter's volcanic moon Io, 5 to 6 meters (16 to 20 feet) per picture element. North is to the top of the images and the entire mosaic spans about 17 kilometers (11 miles) from east to west. The images are rotated relative to one another because of Galileo's great speed as it flies above the surface of Io. The image is centered at 32 degrees north latitude and 193 degrees west longitude</p><p>The Sun illuminates the surface from the right, but topographic shading is difficult to see because of the strong contrasts in brightness of the surface materials. A raised promontory at the bottom of the center image casts shadows into the lower right corner of the left image. Galileo scientists estimate that the promontory is up to 400 meters (one-fourth mile) high.</p><p>The surface is quite varied in appearance, ranging from smooth patches of material to the much rougher top of the promontory. In places, layers of bright and dark material appear to have been exposed by some process of erosion. Sublimation of sulfur-dioxide-rich substances, their transition from solid to gaseous form, may also play a role in the segregation of bright and dark materials. Several intriguing, narrow, channel-like features about 10 meters (11 yards) wide and a few hundred meters (yards) long can be seen. Arrows in the inset indicate some examples of these. These features may provide evidence for springs of some liquid, probably a sulfur compound rather than water.</p><p>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.</p><p>This image and other images and data received from Galileo are posted on the Galileo mission home page at <a href="http://solarsystem.nasa.gov/galileo/" target="_blank">http://solarsystem.nasa.gov/galileo/</a>. Background information and educational context for the images can be found at <a href="http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jup_Io" target="_blank">http://galileo.jpl.nasa.gov/gallery/io.cfm</a>.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02562" onclick="window.open(this.href); return false;" title="Voir l'image PIA02562: Very High Resolution View of Io's Surface sur le site de la NASA">Voir l'image PIA02562: Very High Resolution View of Io's Surface sur le site de la NASA.</a></div>
PIA02562: Very High Resolution View of Io's Surface
<h1>PIA02563: Camaxtli Patera, An Active Volcanic Center on Io</h1><div class="PIA02563" lang="en" style="width:782px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>A hot, active volcanic crater named Camaxtli Patera (large feature to the right) is shown in this image of Jupiter's moon Io taken by NASA's Galileo spacecraft on February 22, 2000.</p><p>A patera is a large depression, probably of volcanic origin, but also affected by cracks and faults in Io's crust. There appear to be both bright and dark lava flows on the patera floor. The dark lava flows are likely to have cooled from super-hot, magnesium-rich, silicate lava of the type that existed on Earth billions of years ago. The bright patches may be much cooler, sulfur-rich lava flows. Bright deposits can also be seen just outside of Camaxtli, and there is a halo of diffuse dark material that extends up to 30 kilometers (19 miles) from the rim of the patera. This halo is probably made up of frozen droplets of lava that rained down after they were blasted into the sky from vents in Camaxtli.</p><p>Two smaller paterae, which are unnamed, are to the left (west) of Camaxtli. One has very dark, very fresh lava on the floor and is hotter than the larger Camaxtli Patera because it is erupting lava at a faster rate. The other is comparatively bright, like the surrounding plains. This implies that the volcanism here has been dormant for long enough that snow and frost have covered the lava flows.</p><p>The surrounding plains are mottled and appear to be topographically rough. The lumpy texture of the ground around Camaxtli appears to be a common feature of the frozen plains of Io. The Sun is almost directly overhead (actually 12 degrees to the south), so most of the brightness variations in this image are due to different types of surface materials rather than topographic shading. The image resolution is 186 meters (204 yards) per picture element and the scene width is 145 kilometers (91 miles). The center of the image is located at about 15 north latitude, 138 west longitude.</p><p>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.</p><p>This image and other images and data received from Galileo are posted on the Galileo mission home page at <a href="http://solarsystem.nasa.gov/galileo/" target="_blank">http://solarsystem.nasa.gov/galileo/</a>. Background information and educational context for the images can be found at <a href="http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jup_Io" target="_blank">http://galileo.jpl.nasa.gov/gallery/io.cfm</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02563" onclick="window.open(this.href); return false;" title="Voir l'image PIA02563: Camaxtli Patera, An Active Volcanic Center on Io sur le site de la NASA">Voir l'image PIA02563: Camaxtli Patera, An Active Volcanic Center on Io sur le site de la NASA.</a></div>
PIA02563: Camaxtli Patera, An Active Volcanic Center on Io
<h1>PIA02564: Io's Prometheus Volcano at Various Resolutions</h1><div class="PIA02564" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>This composite of images, all acquired by NASA's Galileo spacecraft, contains three views at three different image resolutions of the volcano Prometheus on Jupiter's moon Io. The upper mosaic consists of eight high-resolution frames (12 meters or 39 feet per picture element). The lower left image is a single medium-resolution frame (170 meters or 186 yards per picture element); and the lower right mosaic consists of several low-resolution color frames (1.3 kilometers or .81 miles per picture element).</p><p>The high- and medium-resolution frames were obtained during Galileo's third close flyby of Io, on February 22, 2000, while the low-resolution color context frames were obtained on June 30, 1999. In all the images, north is to the top, and the high-resolution mosaic spans about 65 kilometers (40 miles) from east to west. The high-resolution mosaic is centered at about 13 degrees north latitude and 155 degrees west longitude.</p><p>At increasing resolution, more surface details about Prometheus become clear. For example, dark spots visible on flows of Prometheus at lower resolution resolve into dark, fresh lava flows with well-defined margins at higher resolution. Bright spots along the margins of Prometheus resolve into bright streaks that appear to come from plumes emanating from the edges of the Prometheus flows. The terrain surrounding Prometheus, which appears relatively smooth at lower resolution, resolves into a complex material composed of rough, ridge-like features at higher resolution. Also visible in the rightmost frame of the high-resolution mosaic (on the northern edge of the very dark lava flow in the lower right corner) are two bright spots, which may indicate active, glowing lava breakouts.</p><p>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.</p><p>This image, other images and data received from Galileo are posted on the Galileo mission home page at <a href="http://solarsystem.nasa.gov/galileo/" target="_blank">http://solarsystem.nasa.gov/galileo/</a>. Background information and educational context for the images can be found at <a href="http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jup_Io" target="_blank">http://galileo.jpl.nasa.gov/gallery/io.cfm</a>.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02564" onclick="window.open(this.href); return false;" title="Voir l'image PIA02564: Io's Prometheus Volcano at Various Resolutions sur le site de la NASA">Voir l'image PIA02564: Io's Prometheus Volcano at Various Resolutions sur le site de la NASA.</a></div>
PIA02564: Io's Prometheus Volcano at Various Resolutions
<h1>PIA02565: Sources of Volcanic Plumes Near Prometheus</h1><div class="PIA02565" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>Prometheus is the "Old Faithful" of the many active volcanoes on Jupiter's moon Io. A broad, umbrella-shaped plume of gas and dust has been spotted above Prometheus by NASA's Voyager and Galileo spacecraft every time the viewing conditions have been favorable. The volcano is surrounded by a prominent circular ring of bright sulfur dioxide apparently deposited by the plume. However, the origin of Prometheus' plume is a long-standing mystery: Where is the vent that is the source of all the gas and dust?</p><p>Some clues are offered by this false-color picture with a resolution of 170 meters (186 yards) per picture element, which was taken by Galileo on February 22, 2000. To the right is a dark, semi-circular, lava-filled caldera. South of it lies a fissure from which dark lava has flowed toward the west (left). The lava flow extends 90 kilometers (54 miles) from the source. Bright patches probably composed of sulfur dioxide can be seen in several places along the flow's margins. Two of these patches (near the top left edge of the dark lava, at the farthest reaches of the flow) display faint blue hazes, apparently produced by airborne dust entrained within plumes. Both of these spots are locations of newly erupted lava that has encroached on the surrounding plains since Galileo last imaged the region in October 1999. Galileo scientists are now studying whether heating of the volatile, sulfur dioxide-rich plains by encroaching hot lava might account for the persistent plume activity observed near Prometheus.</p><p>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.</p><p>This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at <a href="http://solarsystem.nasa.gov/galileo/" target="_blank">http://solarsystem.nasa.gov/galileo/</a>. Background information and educational context for the images can be found at <a href="http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jup_Io" target="_blank">http://galileo.jpl.nasa.gov/gallery/io.cfm</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02565" onclick="window.open(this.href); return false;" title="Voir l'image PIA02565: Sources of Volcanic Plumes Near Prometheus sur le site de la NASA">Voir l'image PIA02565: Sources of Volcanic Plumes Near Prometheus sur le site de la NASA.</a></div>
PIA02565: Sources of Volcanic Plumes Near Prometheus
<h1>PIA02566: Io's Chain of Craters</h1><div class="PIA02566" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>Most of the 12 images in this mosaic were taken on February 22, 2000, by NASA's Galileo spacecraft. It has been merged with lower-resolution color data acquired by Galileo during the summer of 1999. The mosaic covers the region from Chaac Patera (the green-floored depression on the left side; see Cutout A (below)) to Camaxtli Patera (the depression with a dark halo in upper right; see Cutout B (below)). At least nine other paterae can be seen here.</p><p><a href="/figures/PIA02566a_full.jpg"></a><a href="/figures/PIA02566b_full.jpg"></a><b>Cutout A</b><b>Cutout B</b></p><p>This mosaic illustrates the range of patera morphology on Io. What is a patera? It is an irregular depression, or a complex one with scalloped edges, but which does not have the characteristics of an impact crater. The paterae on Io often correspond to active volcanic centers, and are in some ways similar to calderas. What's a caldera? Calderas are large, usually roughly circular depressions that form by collapse over shallow magma chambers that have been partially emptied by volcanic eruptions. However, the paterae on Io are different from calderas seen elsewhere in the solar system. They have many straight edges and sharp angles, suggesting that they are related to fractures in Io's crust. In many cases the lava can be seen to erupt from these straight edges. Planetary geologists aren't sure whether the paterae form over magma chambers or if they result from fractures and movements in the crust, and the lava subsequently follows the fractures.</p><p>One of the paterae (with orange and white materials--right center; see Cutout C (below)) shows what may be thin plates of crust that have broken off and rafted over a lava lake.</p><p><a href="/figures/PIA02566c_full.jpg"></a><a href="/figures/PIA02566d_full.jpg"></a><b>Cutout C</b><b>Cutout D</b></p><p>Also seen in this mosaic are various dark, bright, and reddish lava flows (towards the upper left but east of Chaac; see Cutout D (above)}) that are not confined to patera floors. The dark flows are associated with high temperatures consistent with silicate compositions. In fact, all the black areas in this mosaic correspond to high-temperature hot spots. The bright flows may have a different composition (such as sulfur) or they may be older silicate flows that have been coated by sulfurous materials.</p><p>The bright plains surrounding the volcanic centers have a bumpy texture. These plains are relatively old, so the roughness may develop slowly over time rather than representing the original topography of volcanic deposits. sublimation of sulfur dioxide is one process that might contribute to the texture.</p><p>The mosaic covers the region from latitude 7 north to 18 north, longitude 130 west to 160 west, with a total width of 850 kilometers (509 miles). The images have a resolution of 186 meters (200 yards) per picture element. The Sun is almost directly overhead (actually 12 degrees to the south), so most of the brightness variations in this image are due to different types of surface materials rather than topographic shading. Colors have been exaggerated.</p><p>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.</p><p>This image and other images and data received from Galileo are posted on the Galileo mission home page at <a href="http://solarsystem.nasa.gov/galileo/" target="_blank">http://solarsystem.nasa.gov/galileo/</a>. Background information and educational context for the images can be found at <a href="http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jup_Io" target="_blank">http://galileo.jpl.nasa.gov/gallery/io.cfm</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02566" onclick="window.open(this.href); return false;" title="Voir l'image PIA02566: Io's Chain of Craters sur le site de la NASA">Voir l'image PIA02566: Io's Chain of Craters sur le site de la NASA.</a></div>
PIA02566: Io's Chain of Craters
PIA02566a_full.jpg
PIA02566a_full.jpg
PIA02566b_full.jpg
PIA02566b_full.jpg
PIA02566c_full.jpg
PIA02566c_full.jpg
PIA02566d_browse.jpg
PIA02566d_browse.jpg
<h1>PIA02567: Giant Lava Flow on Io, in Color</h1><div class="PIA02567" lang="en" style="width:413px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>This mosaic combines images collected in February 2000 and the summer of 1999 by NASA's Galileo spacecraft to highlight new details of the longest active lava flow known in the solar system.</p><p>The area, called Amirani, has been known to be the home of a number of volcanic hot spots ever since NASA's two Voyager spacecraft flew by Jupiter in 1979. Images collected by Galileo in 1999 showed that these hot areas were part of a single immense lava flow field. The newest images confirm that the Amirani flow field is indeed a quilt work of dark lava flows. The most recent lavas are darkest because they are too hot to be covered by sulfur-dioxide plumes. Fresh lava is leaking out of at least five areas at the northern end of the Amirani flow field and at least three places in the middle. However, it is likely that the lava first comes to the surface near the southern end of the flow field. The liquid lava travels under a frozen layer of older lava, breaking out onto the surface only after traveling hundreds of kilometers (hundreds of miles) from the vent. The "small" breakouts produce lava flows larger than the current eruption on Earth at Kilauea Volcano in Hawaii. These observations are helping to explain how very large, ancient lava flows formed on the Earth.</p><p>While the behavior of the lava once it is on the surface makes sense, how it comes to the surface is more complicated. Small, white, diffuse halos surrounding the darkest lava flows are probably sulfur-dioxide-rich snows and frosts that have been vaporized by the hot lava. The bright red material to the south of the Amirani flow field is likely to contain a large fraction of sulfur droplets. Sulfur-rich gas appears to be bubbling out all along the east-west crack at the southern end of Amirani. This may be the crack along which the lava rises to the surface. The main Amirani plume appears to emanate from a fuzzy, purplish area within the southern part of the flow field. This is a plausible alternative location for the lava to come to the surface.</p><p>The mosaic shows an area 500 kilometers (310 miles) long and 180 kilometers (110 miles) wide. Black and white images at 210 meters (690 feet) per picture element were combined with color data at 1.3 kilometers (.8 miles) per picture element. This computer wizardry allows us to learn much more than either set of pictures alone. North is to the top of the picture.</p><p>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.</p><p>This image and other images and data received from Galileo are posted on the Galileo mission home page at <a href="http://solarsystem.nasa.gov/galileo/" target="_blank">http://solarsystem.nasa.gov/galileo/</a>. Background information and educational context for the images can be found at <a href="http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jup_Io" target="_blank">http://galileo.jpl.nasa.gov/gallery/io.cfm</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02567" onclick="window.open(this.href); return false;" title="Voir l'image PIA02567: Giant Lava Flow on Io, in Color sur le site de la NASA">Voir l'image PIA02567: Giant Lava Flow on Io, in Color sur le site de la NASA.</a></div>
PIA02567: Giant Lava Flow on Io, in Color
<h1>PIA02568: Galileo Takes a Close-up Look at Prometheus</h1><div class="PIA02568" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>This high-resolution mosaic of images taken by NASA's Galileo spacecraft shows lava flows, bright streaks, and ridged plains at the northern margin of the lava flow field at the volcanic center Prometheus on Jupiter's moon Io. The images, taken during a flyby of Io on February 22, 2000, have a resolution of 12 meters (39 feet) per picture element.</p><p>The lava is erupting from a fissure about 40 kilometers (25 miles) east (right) of the edge of this mosaic, and the 100 kilometer (62 mile) tall Prometheus plume is erupting from somewhere near the western end of this mosaic. This mosaic was acquired to search for and image the plume vent or vents. We expected to see a small crater surrounded by radial streaks, but no such central vent can be seen in these or other images. Instead, we see bright streaks along the margins of the lava.</p><p>The darkest areas are warm lava flows. Warm lava is dark because it is either too hot or too recent for significant amounts of sulfur-dioxide frost or snow from the plume to have condensed onto it. The blow-up shows two bright dots where hot lava is breaking out of the edge of one of the dark lava flows. The bright, ridged plains to the north of the lava are probably rich in sulfur dioxide. The formation mechanism for the ridges is unclear. The very bright streaks radiating from the area where the lava flows overrun the field are where the hot lava recently vaporized the sulfur dioxide, which then coated the lava-facing sides of the ridges.</p><p>The Prometheus plume has been seen by both the Voyager and Galileo spacecraft whenever the viewing geometry has been favorable. While the morphology of the plume has been nearly constant, the plume's position jumped about 80 kilometers (50 miles) between the Voyager observations in the 1970s and the Galileo observations since 1995. The lava flow field has migrated a similar distance. Galileo scientists are currently investigating whether fresh lava breakouts overrunning plains rich in sulfur dioxide can help explain the plume observations.</p><p>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. Additional information about Galileo and its discoveries is available on the Galileo mission home page at <a href="http://galileo.jpl.nasa.gov" class="external free" target="wpext">http://galileo.jpl.nasa.gov</a>. Background information and educational context for the images can be found at <a href="http://solarsystem.nasa.gov/galileo/gallery/index.cfm" class="external free" target="wpext">http://solarsystem.nasa.gov/galileo/gallery/index.cfm</a>.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02568" onclick="window.open(this.href); return false;" title="Voir l'image PIA02568: Galileo Takes a Close-up Look at Prometheus sur le site de la NASA">Voir l'image PIA02568: Galileo Takes a Close-up Look at Prometheus sur le site de la NASA.</a></div>
PIA02568: Galileo Takes a Close-up Look at Prometheus
<h1>PIA02584: Eruption at Tvashtar Catena on Io</h1><div class="PIA02584" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>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.</p><p>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. </p><p>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.</p><p>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.</p><p>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).</p><p>The individual images in this composite can be viewed separately in <a href="/catalog/PIA02545">PIA02545</a> (left hand image) and <a href="/catalog/PIA02550">PIA02550</a> (right hand image).</p><p>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.</p><p>Images and data received from Galileo are posted on the Galileo mission home page at <a href="http://solarsystem.nasa.gov/galileo/" class="external free" target="wpext">http://solarsystem.nasa.gov/galileo/</a>. Background information and educational context for the images can be found at <a href="http://solarsystem.nasa.gov/galileo/gallery/index.cfm" class="external free" target="wpext">http://solarsystem.nasa.gov/galileo/gallery/index.cfm</a>.</p><p>Images were produced by Brown University, Providence, R.I.,<a href="http://www.planetary.brown.edu/" class="external free" target="wpext">http://www.planetary.brown.edu/</a>, DLR (German Aerospace Center) Berlin,<a href="ttp://www.dlr.de/pf/" class="external free" target="wpext">http://www.dlr.de/pf/</a>, and University of Arizona, Tempe, <a href="http://www.lpl.arizona.edu/" class="external free" target="wpext">http://www.lpl.arizona.edu/</a>.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02584" onclick="window.open(this.href); return false;" title="Voir l'image PIA02584: Eruption at Tvashtar Catena on Io sur le site de la NASA">Voir l'image PIA02584: Eruption at Tvashtar Catena on Io sur le site de la NASA.</a></div>
PIA02584: Eruption at Tvashtar Catena on Io
<h1>PIA02585: Amirani's Big Lava Flow on Io</h1><div class="PIA02585" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>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.</p><p>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 620square 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 60square kilometers (24 square miles) during this time.</p><p>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 100tons 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.</p><p>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.</p><p>Images and data received from Galileo are posted on the Galileo mission home page at <a href="http://solarsystem.nasa.gov/galileo/" class="external free" target="wpext">http://solarsystem.nasa.gov/galileo/</a>. Background information and educational context for the images can be found at <a href="http://solarsystem.nasa.gov/galileo/gallery/index.cfm" class="external free" target="wpext">http://solarsystem.nasa.gov/galileo/gallery/index.cfm</a>.</p><p>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.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02585" onclick="window.open(this.href); return false;" title="Voir l'image PIA02585: Amirani's Big Lava Flow on Io sur le site de la NASA">Voir l'image PIA02585: Amirani's Big Lava Flow on Io sur le site de la NASA.</a></div>
PIA02585: Amirani's Big Lava Flow on Io
<h1>PIA02586: Tohil Mons, Io</h1><div class="PIA02586" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>Images taken at different times and from different positions by NASA's Galileo spacecraft provide information about the three-dimensional structure of a large mountain named Tohil Mons on Jupiter's moon Io.</p><p>The first part of this image package is a mosaic combining detailed images that were taken a year ago by Galileo on Feb. 22, 2000, with a lower-resolution image of a wider area taken on June 30, 1999. The sharper portion has a resolution of 165 meters (540 feet) per picture element. The lower-resolution context image is at 1.3 kilometers (0.8 mile) per picture element. North is to the top of the image. The Sun was almost directly behind the spacecraft, so shadows aren't visible.</p><p>Because topography is difficult to distinguish on Io unless the Sun is low enough to cast shadows, the second part of this release is a stereo image of Tohil Mons that was created from two mosaics acquired on Oct.11, 1999, and Feb. 22, 2000. When viewed with red-blue glasses, it illustrates the three-dimensional shape of the mountain and two nearby volcanic depressions, which are called paterae. The largest patera lies along the northeastern margin of the mountain. The stereo observation reveals that the smaller patera with the dark floor is surrounded by mountainous walls. The black lines are areas where data were not acquired.</p><p><a href="/figures/PIA02586b_full.jpg"></a></p><p>To the southeast of the peak, many bright lines trending northwest-southeast can be seen. Since the two individual images were taken when the Sun was quite high, it was difficult to determine the relationship between the bright material and the topography. The stereo image reveals that the light material is concentrated at the bases of cliffs. This series of cliffs appears step-like, which may indicate layering in Io's crust.</p><p>Two additional figures describing the three-dimensional shape of the Tohil Mons region are also included. The first of these is a topographic representation of what Tohil Mons looks like when seen from the northeast. The topography has been vertically exaggerated. The peak's height is about 5.4 kilometers, plus or minus 1.1 kilometer (about 18,000 feet, give or take 3,600 feet).</p><p><a href="/figures/PIA02586c_full.jpg"></a></p><p>The second figure shows two views in which Tohil Mons has been outlined in red. The top image was taken at low resolution and a low Sun angle during Galileo's third orbit, in 1996. Because the Sun is low, topographic features on the mountain can be recognized from the shadows they cast. The two paterae and the peak of the mountain are labeled. The bottom image was taken on Feb. 22, 2000, at higher resolution and a higher Sun angle. The topography is almost indistinguishable, but many more details can be discerned. By combining several observations in this manner, Galileo scientists are able to study Io's mountains and to learn about their evolution and their relationship to Io's volcanoes.</p><p><a href="/figures/PIA02586d_full.jpg"></a></p><p>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.</p><p>This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at <a href="http://solarsystem.nasa.gov/galileo/" class="external free" target="wpext">http://solarsystem.nasa.gov/galileo/</a>. Background information and educational context for the images can be found at <a href="http://solarsystem.nasa.gov/galileo/gallery/index.cfm" class="external free" target="wpext">http://solarsystem.nasa.gov/galileo/gallery/index.cfm</a>.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02586" onclick="window.open(this.href); return false;" title="Voir l'image PIA02586: Tohil Mons, Io sur le site de la NASA">Voir l'image PIA02586: Tohil Mons, Io sur le site de la NASA.</a></div>
PIA02586: Tohil Mons, Io
<h1>PIA02588: Galileo and Cassini Image Two Giant Plumes on Io</h1><div class="PIA02588" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>Two tall volcanic plumes and the rings of red material they have deposited onto surrounding surface areas appear in images taken of Jupiter's moon Io by NASA's Galileo and Cassini spacecraft in late December 2000 and early January 2001.</p><p>A plume near Io's equator comes from the volcano Pele. It has been active for at least four years, and has been far larger than any other plume seen on Io, until now. The other, nearer to Io's north pole, is a Pele-sized plume that had never been seen before, a fresh eruption from the Tvashtar Catena volcanic area.<p></p>The observations were made during joint studies of the Jupiter system while Cassini was passing Jupiter on its way to Saturn. The two craft offered complementary advantages for observing Io, the most volcanically active body in the solar system. Galileo passed closer to Io for higher-resolution images, and Cassini acquired images at ultraviolet wavelengths, better for detecting active volcanic plumes.</p><p>The Cassini ultraviolet images, upper right, reveal two gigantic, actively erupting plumes of gas and dust. Near the equator, just the top of Pele's plume is visible where it projects into sunlight. None of it would be illuminated if it were less than 240 kilometers (150 miles) high. These images indicate a total height for Pele of 390kilometers (242 miles). The Cassini image at far right shows a bright spot over Pele's vent. Although the Pele hot spot has a high temperature, silicate lava cannot be hot enough to explain a bright spot in the ultraviolet, so the origin of this bright spot is a mystery, but it may indicate that Pele was unusually active.</p><p>Also visible is a plume near Io's north pole. Although 15 active plumes over Io's equatorial regions have been detected in hundreds of images from NASA's Voyager and Galileo spacecraft, this is the first image ever acquired of an active plume over a polar region of Io. The plume projects about 150 kilometers (about 90 miles) over the limb, the edge of the globe. If it were erupting from a point on the limb, it would be only slightly larger than a typical Ionian plume, but the image does not reveal whether the source is actually at the limb or beyond it, out of view.</p><p>A distinctive feature in Galileo images since 1997 has been a giant red ring of Pele plume deposits about 1,400 kilometers (870 miles) in diameter. The Pele ring is seen again in one of the new Galileo images, lower left. When the new Galileo images were returned this month, scientists were astonished to see a second giant red ring on Io, centered around Tvashtar Catena at 63 degrees north latitude. (To see a comparison from before the ring was deposited, see <a href="/catalog/PIA01604">PIA01604</a> or <a href="/catalog/PIA02309">PIA02309</a>.) Tvashtar was the site of an active curtain of high-temperature silicate lava imaged by Galileo in November 1999 and February 2000 (image <a href="/catalog/PIA02584">PIA02584</a>). The new ring shows that Tvashtar must be the vent for the north polar plume imaged by Cassini from the other side of Io! This means the plume is actually about 385 kilometers (239 miles) high, just like Pele. The uncertainty in estimating the height is about 30 kilometers (19 miles), so the plume could be anywhere from 355 to 415 kilometers (221 to 259 miles) high.</p><p>If this new plume deposit is just one millimeter (four one-hundredths of an inch) thick, then the eruption produced more ash than the 1980 eruption of Mount St. Helens in Washington.</p><p>NASA recently approved a third extension of the Galileo mission, including a pass over Io's north pole in August 2001. The spacecraft's trajectory will pass directly over Tvashtar at an altitude of 200 kilometers (124 miles). Will Galileo fly through an active plume? That depends on whether this eruption is long-lived, like Pele, or brief, and it also depends on how high the plume is next August. Two Pele-sized plumes are inferred to have erupted in 1979 during the four months between Voyager 1 and Voyager 2 flybys, as indicated by new Pele-sized rings in Voyager 2 images. Those eruptions, both from high-latitude locations, were shorter-lived than Pele, but their actual durations are unknown. Before its August flyby, Galileo will get another more-distant look at Tvashtar in May.</p><p>It has been said that Io is the heartbeat of the Jovian magnetosphere. The two giant plumes evidenced in these images may have had significant effects on the types, density and distribution of neutral and charged particles in the Jupiter system during the joint observations of the system by Galileo and Cassini from November 2000 to March 2001.</p><p>These Cassini images were acquired on Jan. 2, 2001, except for the frame at the far right, which was acquired a day earlier. The Galileo images were acquired on Dec. 30 and 31, 2000. Cassini was about 10 million kilometers (6 million miles) from Io, ten times farther than Galileo.</p><p>More information about the Cassini and Galileo joint observations of the Jupiter system is available online at <a href="http://www.jpl.nasa.gov/jupiterflyby">http://www.jpl.nasa.gov/jupiterflyby</a>.</p><p>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 Galileo and Cassini missions for NASA's Office of Space Science, Washington, D.C.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02588" onclick="window.open(this.href); return false;" title="Voir l'image PIA02588: Galileo and Cassini Image Two Giant Plumes on Io sur le site de la NASA">Voir l'image PIA02588: Galileo and Cassini Image Two Giant Plumes on Io sur le site de la NASA.</a></div>
PIA02588: Galileo and Cassini Image Two Giant Plumes on Io
<h1>PIA02589: Io's Nighttime Heat</h1><div class="PIA02589" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>Powerful volcanoes and the previous day's sunshine warm the nighttime surface of Jupiter's moon Io, as seen in this image from NASA's Galileo spacecraft.<p>The left-hand frame shows the best view that Galileo has yet provided of Io's nighttime temperatures. For reference, the right hand frame, based on Galileo camera images, shows the same hemisphere of Io in visible light. The thin bright crescent indicates the only observable portion illuminated by sunlight during the temperature measurements. Several volcanoes are identified on both images: L-K is Lei-Kung Fluctus, L is Loki, Pi is Pillan, M is Marduk, and Pe is Pele.<p>The temperature map comes from observations by Galileo's photopolarimeter-radiometer instrument during the spacecraft's 27th orbit of Jupiter, in February 2000. Blue indicates the coldest temperatures, near 90 degrees Kelvin (minus 297 degrees Fahrenheit), while oranges and yellows indicate the highest temperatures, in excess of 170 K (minus 153 F). Small areas of the volcanoes are far hotter than this, exceeding 1,500 K (2,240 F). However, in this relatively low-resolution view, which shows no features smaller than about 340 kilometers (210 miles) across, radiation from these small, hot regions is mixed with radiation from surrounding colder regions, so the high temperatures are not detected directly. The observation was made without a filter, so it measures the total heat radiation from Io's night side at all wavelengths.<p>Much of the heat comes from a few discrete volcanoes. The brightest is Loki, which radiates roughly 15 percent of Io's total volcanic heat, and would appear much brighter still were it not for severe foreshortening due to its position near the edge of the disk. Second brightest is Pillan, where the heat is radiated by extensive cooling lava flows produced largely by an eruption witnessed by Galileo in June 1997 and later. In contrast, although the volcano Pele spouts Io's largest plume, which produces the large orange ring seen in the right-hand image, Pele emits very little total heat. This is because Pele's activity, though vigorous, is confined to a small volcanic crater, where there is no room for large, warm lava flows to radiate heat.<p>The cooler regions, shown in blues and purples, are dominated by radiation from the surface between the volcanoes, which was warmed by sunlight the previous day and retains some of that heat through the night. Because high-latitude regions receive less sunlight during the day, we would expect them to be cooler at night, but the image shows that temperature varies little with latitude, which is puzzling. Perhaps excess volcanic heat is radiated at the poles, or the polar regions are composed of surface materials that cool off less at night than the materials at lower latitudes. Also, viewing the poles from this angle preferentially presents slopes that were tilted towards the Sun during the day, and thus received more sunlight than the average surface, and this effect might also contribute to the apparent warmth near the poles. The photopolarimeter-radiometer observations of the polar regions on subsequent Io flybys may clear up this mystery.<p>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. Additional information about Galileo and its discoveries is available on the Galileo mission home page at <a href="http://solarsystem.nasa.gov/galileo/" target="_blank">http://solarsystem.nasa.gov/galileo/</a>.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02589" onclick="window.open(this.href); return false;" title="Voir l'image PIA02589: Io's Nighttime Heat sur le site de la NASA">Voir l'image PIA02589: Io's Nighttime Heat sur le site de la NASA.</a></div>
PIA02589: Io's Nighttime Heat
<h1>PIA02592: Northern Plume and Plume Deposits on Io</h1><div class="PIA02592" lang="en" style="width:690px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>Backlit views (left pair) show a giant volcanic plume as a bulge on the crescent edge of Jupiter's moon Io, and more fully lit views (right pair) reveal rings where sulfur-rich plume material has fallen back to the ground, in images captured by NASA's Galileo spacecraft in early August 2001.<p>Io is the most volcanically active world known. Galileo and NASA's Voyager and Cassini spacecraft have caught several of Io's volcanoes in action lofting plumes of gas and particles high above the large moon's surface. However, none of the plumes seen previously has climbed as high as the one evidenced in three of these pictures.<p>During its Aug. 6, 2001, close encounter with Io, Galileo flew right through a space where a plume from the Tvashtar volcano near Io's north pole had been active when Galileo and Saturn-bound Cassini imaged Io seven months earlier. To see if the Tvashtar plume was still active in August, scientists used Galileo's camera to acquire images when the spacecraft was nearly on the opposite side of Io from the Sun, so that Io appears as a backlit crescent.<p>Tvashtar's plume did not show up, but another one did, rising from a previously undiscovered and still unnamed volcano about 600 kilometers (370 miles) south of Tvashtar. The left two images are color coded to reveal the faint outer plume. The bright inner plume rises about 150 kilometers (90 miles) high, and the top of the faint outer plume can be detected at 500 kilometers (310 miles) above the surface, making this is the largest plume ever detected on Io. A portion of the plume with intermediate brightness extends north of the eruption's source vent. (The vertical lines, bright spots and short streaks in these two images are noise.)<p>One of the more fully illuminated color images of Io (second image from right) reveals a bull's-eye ring of new dark and light materials marking the eruption site. No obvious volcanic center had previously been seen at this location, 41 degrees north latitude and 133 degrees west longitude. The bright material of the new plume deposit overlies the red-ring plume deposit encircling the Tvashtar volcano at 63 degrees north, 123 degrees west. Tvashtar's ring deposit was first seen in Galileo images taken in late December 2000.<p>Another new full-disc color image of Io (far right) reveals yet another new plume deposit near Io's north pole, encircling the Dazhbog Patera volcanic site. This red ring has a diameter of about 1,000 kilometers (620 miles), suggesting a plume height of about 300 kilometers (190 miles). This plume deposit was not present in January 2001, so it is evidence of a new eruption.<p>Io is about the same size as Earth's Moon. All four images have resolutions of 18 to 20 kilometers (11 to 12 miles) per picture element. Unlabeled versions are also available. Click on the thumbnail versions below.<p><a href="/figures/PIA02592_nlbl_full.jpg"></a><a href="/figures/PIA02592_nims_full.jpg"></a><a href="/figures/PIA02592_ssi_full.jpg"></a><p>Infrared imagery from Galileo or Earth-based telescopes has detected intense hot spots at the sites of all three of these giant plumes. Giant polar plumes represent a class of eruption seen by the Voyager spacecraft in 1979, but not during Galileo's first five years of orbiting Jupiter. Voyager was unable to measure temperatures or other properties of these eruptions, so scientists are pleased Galileo has survived long enough to do so. Galileo reached Jupiter in late 1995. Its original two-year orbital mission has been extended three times to take advantage of the spacecraft's continuing capability to return valuable scientific information about the Jupiter system.<p>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. Additional information about Galileo and its discoveries is available on the Galileo mission home page at <a href="http://solarsystem.nasa.gov/galileo/" target="_blank">http://solarsystem.nasa.gov/galileo/</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02592" onclick="window.open(this.href); return false;" title="Voir l'image PIA02592: Northern Plume and Plume Deposits on Io sur le site de la NASA">Voir l'image PIA02592: Northern Plume and Plume Deposits on Io sur le site de la NASA.</a></div>
PIA02592: Northern Plume and Plume Deposits on Io
<h1>PIA02597: Slumping Cliff on Io in High Resolution</h1><div class="PIA02597" lang="en" style="width:798px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>A cliff slumps outward in these high-resolution views that NASA's Galileo spacecraft captured the edge of a mountain named Telegonus Mensa on Jupiter's moon Io.<p>When Galileo flew near the south pole of Io in October 2001, scientist's targeted this cliff to study the process of erosion. Water and wind cause most erosion on Earth, but Io has neither surface water nor an atmosphere. The cliff is slumping due to gravity.<p>The smaller picture (top) has a resolution of 10 meters (33 feet) per picture element. Galileo's camera took it from a distance of about 1,000 kilometers (620 miles). The larger image (below) sets context with a resolution of 40 meters (131 feet) per picture element and was taken from a distance of about 4,200 kilometers (2,600 miles). North is to the top and the Sun illuminates the surface from the upper right.<p><a href="/figures/PIA02597_cntxt.tif"></a><a href="/figures/PIA02597_cntxt_full.jpg"></a>tiff Filejpeg File<p>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. Additional information about Galileo and its discoveries is available on the Galileo mission home page at <a href="http://galileo.jpl.nasa.gov/">http://galileo.jpl.nasa.gov/</a>. Background information and educational context for the images can be found at <a href="http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jup_Io" class="external free" target="wpext">http://solarsystem.nasa.gov/galileo/gallery/io.cfm</a>.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02597" onclick="window.open(this.href); return false;" title="Voir l'image PIA02597: Slumping Cliff on Io in High Resolution sur le site de la NASA">Voir l'image PIA02597: Slumping Cliff on Io in High Resolution sur le site de la NASA.</a></div>
PIA02597: Slumping Cliff on Io in High Resolution
<h1>PIA02598: Lava Channel at Io's Emakong Patera</h1><div class="PIA02598" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>Clues about how lava spreads great distances on Jupiter's volcanic moon Io come from high-resolution views taken by NASA's Galileo spacecraft of a lava channel flowing out of Emakong Patera near Io's equator.<p>The lava channel is dark and runs to the right from the dark patera, or large depression, at the left of this mosaic. The mosaic sets several high-resolution images (30 meters or 100 feet per picture element) into the context of lower-resolution images (150 meters or 490 feet per picture element). Galileo took the high-resolution ones during a close flyby of Io on Oct. 15, 2001. The <a href="/catalog/PIA02539">context images</a> of the Emakong Patera region were acquired during a November 1999 flyby.<p>The 1999 images showed a dark channel though which molten material once fed a broad, bright lava flow that extended for hundreds of kilometers or miles. Those images raised questions about how lava could travel so far. The new images show that the lava channel is roofed over in several places, indicating that an insulating cover grew over parts of the channel, allowing the lava to move farther before freezing. More puzzling is the intimate mixing of bright and dark material in the lava flow. The liquids might have been a combination of molten rock and sulfur or might have been just sulfur, which has black, red, orange and yellow forms. One possibility is that the material that erupted from the volcano was molten rock that melted an underlying layer of sulfur. The molten sulfur could then have oozed up through the solidifying lava, producing the mottled surface seen here.<p>North is to the top of the picture. The Sun illuminates the surface from almost directly behind the spacecraft, so the brightness variations in the image are due to differences in the brightness of surface materials, not to shadows. The view is centered at 4.6 degrees south latitude and 117.5 degrees west longitude.<p>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. Additional information about Galileo and its discoveries is available on the Galileo mission home page at http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at <a href="http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jup_Io" target="_blank">http://galileo.jpl.nasa.gov/gallery/io.cfm</a>.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02598" onclick="window.open(this.href); return false;" title="Voir l'image PIA02598: Lava Channel at Io's Emakong Patera sur le site de la NASA">Voir l'image PIA02598: Lava Channel at Io's Emakong Patera sur le site de la NASA.</a></div>
PIA02598: Lava Channel at Io's Emakong Patera