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

<h1>PIA02319: Closeups of Io (false color)</h1><div class="PIA02319" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>NASA's Galileo spacecraft acquired its highest resolution images of Jupiter's volcanic moon Io on July 3, 1999 during its closest pass by Io since it entered orbit around Jupiter in December 1995. This color mosaic uses the near-infrared, green and violet filters (slightly more than the visible range) of the spacecraft's camera, processed to enhance more subtle color variations. Most of Io's surface has pastel colors, punctuated by black, brown, green, orange, and red areas near the active volcanic centers.</p><p>The improved resolution reveals small-scale color areas which were not recognized previously and which suggest that the lava and sulfurous deposits are composed of complex mixtures (close-up A). Some of the bright, whitish, high-latitude (near the top and bottom) deposits have an ethereal quality like a transparent covering of frost (close-up B). Bright red areas were seen in previous images only as diffuse deposits. However, they now appear as both diffuse deposits and sharp linear features like fissures (close-up C). Some volcanic centers have bright and colorful flows, perhaps due to flows of sulfur (rather than silicate) lava (close-up D). In this region of Io, bright, white material can also be seen to emanate from linear rifts and cliffs.</p><p>Comparison of this mosaic to <a href="http://www2.jpl.nasa.gov/galileo/sepo/" target="_blank">http://www.jpl.nasa.gov/galileo/sepo</a>./atjup/io/color.html">previous Galileo images</a> reveals many changes due to ongoing volcanic activity.</p><p>Galileo is scheduled to make two close passes of Io in October and November. Most of the high-resolution targets for these flybys are seen on the hemisphere shown here.</p><p>North is to the top of the picture, and the Sun illuminates the surface from almost directly behind the spacecraft. This illumination is good for imaging color variations, but poor for imaging topographic shading. However, some topographic shading can be seen here due to the combination of relatively high resolution (1.3 kilometers or 0.8 miles per picture element) and rugged topography over parts of Io. The mosaic is centered at 0.3 degrees north latitude and 137.5 degrees west longitude. The images were taken at a distance of about 130,000 kilometers (81,000 miles) by Galileo's onboard solid state imaging camera.</p><p>The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC.</p><p>This image and other images and data received from Galileo are posted on the World Wide Web at URL <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://www2.jpl.nasa.gov/galileo/sepo/" target="_blank">http://www.jpl.nasa.gov/galileo/sepo</a><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02319" onclick="window.open(this.href); return false;" title="Voir l'image PIA02319: Closeups of Io (false color) sur le site de la NASA">Voir l'image PIA02319: Closeups of Io (false color) sur le site de la NASA.</a></div>
PIA02319: Closeups of Io (false color)
<h1>PIA02501: Changes at Pillan Patera</h1><div class="PIA02501" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>Dramatic changes have occurred at the volcanically active Pillan Patera region of Jupiter's moon Io over the past three years, as seen in this set of three images taken by NASA¹s Galileo spacecraft.</p><p>The image on the left was taken in <a href="/catalog/PIA00738">April 1997. The middle image shows the same area in <a href="/catalog/PIA01667">September 1997</a> after a huge eruption occurred. The eruption produced the large, dark deposit just above and to the right of the center. The deposit, which is 400 kilometers (250 miles) in diameter, surrounds Pillan Patera and covers part of the bright red ring, which is the deposit from Pele¹s plume.</p><p>The image on the right was acquired in July 1999 and is our best view of the region since 1997. It shows changes that have taken place on the surface since the eruption almost two years ago. The red material from Pele, which probably contains some form of sulfur, has started to cover, but has not yet entirely obscured, the dark material around Pillan. This may indicate that the plumes of both Pillan and Pele are still active. This image also shows that a small, unnamed volcano to the right of Pillan has erupted, depositing dark material surrounded by a yellow ring, which is most visible where it covers some of the dark material from Pillan's 1997 eruption.</p><p>Some of the color differences between the three images are the effects of different lighting conditions when the images were taken. The apparent change in brightness of the dark feature in the lower left corner (Babbar Patera) and of parts of Pele's red plume deposit, are thought to be due to changes in illumination. However, such illumination changes cannot explain the dramatic changes seen at Pillan.</p><p>Filters in red, green, and violet wavelengths were combined to produce these images. The color range is slightly enhanced from what the human eye might see at Io. North is to the top of the picture, and the Sun illuminates the surface from the right on the first image, and from the left for the other two. The images are centered at 19 degrees south latitude and 250 degrees west longitude and cover an area approximately 1,650 kilometers wide and 1,750 kilometers high (1,025 miles and 1,090 miles). The resolution of the images on the left and right is about 12 kilometers (7 miles) per picture element. The middle image has a slightly better resolution of about 5 kilometers (3 miles) per picture element. The images taken on April 4, 1997 were from a range of 600,486 kilometers (375,304 miles) by Galileo¹s camera. The images taken on September 19, 1997, were from a range of 505,628 kilometers (316,017 miles). The July 2, 1999 images were taken from a distance of 585,452 kilometers (365,908 miles).</p><a href="/figures/io_traj_full.jpg"></a>Click on this image to view <br> Galileo's flight plan for I24 & I25.<br>(MRPS95336)<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 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://www2.jpl.nasa.gov/galileo/sepo/" target="_blank">http://www.jpl.nasa.gov/galileo/sepo</a>."><a href="http://www2.jpl.nasa.gov/galileo/sepo/" target="_blank">http://www.jpl.nasa.gov/galileo/sepo</a>.</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02501" onclick="window.open(this.href); return false;" title="Voir l'image PIA02501: Changes at Pillan Patera sur le site de la NASA">Voir l'image PIA02501: Changes at Pillan Patera sur le site de la NASA.</a></div>
PIA02501: Changes at Pillan Patera
<h1>PIA02502: Masubi Plume on Io</h1><div class="PIA02502" lang="en" style="width:329px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>A plume of gas and particles is ejected some 100 kilometers (about 60 miles) above the surface of Jupiter's volcanic moon Io in this color image, recently taken by NASA¹s Galileo spacecraft.</p><p>The plume is erupting from near the location of a plume first observed by the Voyager spacecraft in 1979 and named Masubi. However, during the course of the Galileo tour of Jupiter and its moons, a plume <a href="/catalog/PIA02503">has appeared at different locations</a> within the Masubi region.</p><p>This color image is the same as the <a href="/catalog/PIA02309">previously released false color mosaic of Io</a>, but with special processing to enhance the visibility of the plume. The plume appears blue because of the way small particles in the plume scatter light.</p><p>North is to the top of the picture, and the Sun illuminates the surface from almost directly behind the spacecraft. The resolution is 1.3 kilometers (0.8 miles) per picture element. The images were taken on July 3, 1999 at a distance of about 130,000 kilometers (81,000 miles) by the Galileo¹s camera.</p><br>(P50590, MRPS95297)<br><p>The two images on the left are actually the same image displayed indifferent ways. In the top-left image, the Masubi plume is too dim to be seen. The bottom-left image has been processed to enhance the visibility of the plume, which can be seen rising above the bottom-left edge of Io's disk. This processing overexposes the surface of Io so it appears completely white. In the pair of images on the right, a second image has been processed in similar fashion, so that Io's surface features are visible in the top-right image and are overexposed in the bottom-right image. This time Masubi is on the night side of Io, just beyond the terminator (the imaginary line separating day from night), but the plume is high enough that it extends up into the sunlight. A plume from the volcano<a href="/catalog/PIA02505">Prometheus</a> can also be seen in this image, rising above the left edge of Io's disk. The diagonal line in the bottom-right image and the small bright spots sprinkled across all the images are caused by charged particles hitting the camera's CCD (charge-coupled device) detector.</p><p>North is to the top in all the images. The images on the left were taken by the on August 14, 1999 at a range of 1.1 million kilometers (700,000 miles) and have a resolution of 11 kilometers (7 miles) per picture element. The sun illuminates the surface from behind the spacecraft. The images on the right were taken on August 14, 1999 at a range of 1.6 million kilometers (1 million miles) and have a resolution of 16 kilometers (10 miles) per picture element. The sun illuminates the surface from the left.</p><a href="/figures/io_traj_full.jpg"></a>Click on this image to view <br> Galileo's flight plan for I24 & I25.<br>(MRPS95336)<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 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://www2.jpl.nasa.gov/galileo/sepo/" target="_blank">http://www.jpl.nasa.gov/galileo/sepo</a>."><a href="http://www2.jpl.nasa.gov/galileo/sepo/" target="_blank">http://www.jpl.nasa.gov/galileo/sepo</a>.</a></p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02502" onclick="window.open(this.href); return false;" title="Voir l'image PIA02502: Masubi Plume on Io sur le site de la NASA">Voir l'image PIA02502: Masubi Plume on Io sur le site de la NASA.</a></div>
PIA02502: Masubi Plume on Io
<h1>PIA02503: Migrating Volcanic Plumes on Io</h1><div class="PIA02503" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>This set of four images, taken by NASA's Galileo spacecraft, shows a sequence of volcanic activity on Jupiter's moon Io over the last two years. As seen from left to right, the feature called <a href="/catalog/PIA02502">Masubi</a> was observed during Galileo¹s 9th, 10th, 15th, and 22nd orbits of Jupiter. These images show that a plume deposit from Masubi appears in September 1997 and has disappeared eight months later, only to reappear in a different place little more than a year later. The deposit, which originated from a volcanic vent, contains snow rich in sulfur dioxide.</p><p>Plume deposits are formed when material is blown out of a vent in a continuous, geyser-like, high-velocity eruption, with the material then falling back to Io's surface under the influence of gravity. When it hits the surface, it forms a symmetric ring surrounding the plume vent. The plume deposits are transient features, present only while the associated plume is active and for a brief time afterwards. This sequence of images suggests that the plume deposit visible during Galileo¹s 10th orbit was almost completely gone by the time of its 15th orbit, eight months later. This illustrates how ephemeral the deposits are.</p><p>Scientists are intrigued by the speed at which the active plume location seems to have migrated. The distance between the centers of the deposits visible in the images from the 10th orbit, second from left, and 22nd orbit, the image on the right, (occurring over a period of less than two years), is about 125 kilometers (78 miles). The plume deposit has changed in size as well as location. The four arrows are the same size and orientation in the images from the 10th and 22nd orbit, showing that the dark ring of material is larger during the 22nd orbit than it was in the 10th orbit.</p><p>These images were taken through the violet filter of Galileo¹s camera. North is to the top and the Sun illuminates the surface from the left in the images from June 1997 and August 1999, and from the right in the images from September 1997 and May 1998. The images are centered at 50 degrees south latitude and 54 degrees west longitude and cover an area approximately 750 kilometers (470 miles) wide and 1,050 kilometers (660 miles) high. From left to right, the image resolutions are: 16 kilometers (10 miles), 10 kilometers (6.2 miles), 14 kilometers (8 miles), and, 16 kilometers (10 miles) per picture element.</p><p>From left to right, the images were taken by Galileo¹s camera on the following dates from the following distances from Io: June 17, 1997, at 816,500 kilometers (507,300 miles); September 18, 1997, at 1,046,500 kilometers (650,300 miles); May 30, 1998, at 1,398,500 kilometers (869,000 miles); and August 13, 1999, at 1,565,000 kilometers (972,400).</p><a href="/figures/io_traj_full.jpg"></a>Click on this image to view <br> Galileo's flight plan for I24 & I25.<br>(MRPS95336)<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 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://www2.jpl.nasa.gov/galileo/sepo/" target="_blank">http://www.jpl.nasa.gov/galileo/sepo</a><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02503" onclick="window.open(this.href); return false;" title="Voir l'image PIA02503: Migrating Volcanic Plumes on Io sur le site de la NASA">Voir l'image PIA02503: Migrating Volcanic Plumes on Io sur le site de la NASA.</a></div>
PIA02503: Migrating Volcanic Plumes on Io
<h1>PIA02504: Close-up of Zamama, Io (color)</h1><div class="PIA02504" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>A volcano named Zamama on Jupiter's moon Io has recently changed in appearance as seen in this pair of images of Io acquired by NASA's Galileo spacecraft as it approached Io in preparation for a close flyby.</p><p>The false color images use the near-infrared, green and violet filters (a range greater than the range the human eye can see) of the spacecraft's camera, processed to slightly enhance Io's naturally vibrant colors. The image on the left was acquired in March 1998 during Galileo's 14th orbit and the image on the right was collected in July 1999 during the 21st orbit. The July 1999 images are the highest resolution images of Io taken by Galileo since it entered orbit around Jupiter in December 1995.</p><p><a href="/catalog/PIA01071">Zamama formed</a> during the time period between the flybys of NASA's Voyager spacecraft in 1979 and Galileo's first images of Io taken in 1996. Based on these images, Galileo scientists suspect that the dark lava is erupting from a crack in the ground. Analysis of combined data from Galileo's camera and its near-infrared mapping spectrometer instrument showed that the lava erupting at Zamama must be hotter than 830 C (1,500 F). Because this too hot to be sulfur, scientists believe the lava may contain silicates.</p><p>The most dramatic difference between these two images is that the volcanic plume that was active in March 1998 and earlier had stopped erupting by July 1999. The rising core of the umbrella-shaped plume can be seen in the 1998 image as a bluish spot in the center of the dark lava. Dark and bright spokes of material falling away from the core are also visible. When it falls back to the ground, this material makes circular white and yellow deposits around the vent. The white deposits are thought to be composed mostly of sulfur dioxide that left the volcanic vent as a vapor and condensed into a frost as the gases expanded into the near-vacuum of Io's atmosphere. Interestingly, red plume material has only been deposited to the northwest. This might be the result of small pockets of boiling sulfur that produce droplets of red sulfur blown outward by the main plume. Most of the other, more subtle color variations around Zamama are likely to be the result of different lighting conditions that existed when the two images were taken.</p><p>A high-resolution (20 to 40 meters or 66 to 130 feet per picture element) strip of images across Zamama is planned during Galileo's flyby of Io on October 10, 1999. These images will be useful in determining how lava moves on Io's surface, specifically whether the lava travels in open rivers of lava or in well-insulated lava tubes. The size and shape of features on the lava flows can be used to estimate properties of the lava that will provide vital clues to the still unanswered question about what kind of lava is erupting from Io's volcanoes.</p><p>North is to the top of the pictures. The images are centered at 17.4 degrees north latitude and 173 degrees west longitude. The image on the left was taken on March 1998 at a range of 294,000 kilometers (183,000 miles) and has a resolution of 3 kilometers (2 miles) per picture element. The Sun illuminates the surface from the right. The image on the right was taken in July 1999 at a distance of about 130,000 kilometers (81,000 miles) and has a resolution of 1.3 kilometers or 0.8 miles per picture element. The Sun illuminates the surface from almost directly behind the spacecraft.</p><a href="/figures/zamama_full.jpg"></a>Click on this image to view <br> a context image of Io's <br> Zamama volcano.<br>(MRPS95333)<a href="/figures/io_traj_full.jpg"></a>Click on this image to view <br> Galileo's flight plan for I24 & I25.<br>(MRPS95336)<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 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://www2.jpl.nasa.gov/galileo/sepo/" target="_blank">http://www.jpl.nasa.gov/galileo/sepo</a><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02504" onclick="window.open(this.href); return false;" title="Voir l'image PIA02504: Close-up of Zamama, Io (color) sur le site de la NASA">Voir l'image PIA02504: Close-up of Zamama, Io (color) sur le site de la NASA.</a></div>
PIA02504: Close-up of Zamama, Io (color)
<h1>PIA02505: Close-up of Prometheus, Io (color)</h1><div class="PIA02505" lang="en" style="width:398px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>The volcano called Prometheus, found on Jupiter's moon Io, could be called the Old Faithful of the outer solar system, because its volcanic plume has been visible every time it has been observed since 1979. This particular image, one of the highest-resolution pictures ever taken of Io, was obtained by NASA's Galileo spacecraft as it approached Io on July 3, 1999.</p><p>The volcanic plume of Prometheus has been visible during observations by Galileo (<a href="/catalog/PIA00495">1996</a>-1999) and NASA's Voyager spacecraft (1979). No other volcano on Io has been so stable in its behavior. However, between the Voyager flybys and the time of Galileo's arrival at Jupiter, the source of the plume has shifted about 70 kilometers (44 miles) to the west.</p><p>This false color close-up was taken of Prometheus using the near-infrared, green and violet filters (slightly greater than the visible range) of the spacecraft's camera and processed to enhance subtle color variations.</p><p>The long-lived plume has produced a ring-like deposit of bright white and yellow material that is likely to be rich in sulfur dioxide frost. Also note the denser jets in the plume that point like spokes to its source. Galileo scientists do not yet know whether this long-lived plume is erupting from a vent at the west end of the lava flow, or if the plume is being produced by the advancing lava as it flows over ground rich in sulfur dioxide.</p><p>Galileo will acquire black and white images of the Prometheus at resolutions between 35 to 70 meters (120 to 230 feet) per picture element and color images at resolutions of about 230 meters (750 feet) per picture element during its close flyby of Jupiter's moon Io on the evening of October 10, 1999 (Pacific time). These images will be important in understanding how volcanic plumes form on Io. In particular, we are interested in seeing if the plume material is escaping from Io's interior or from the surface at the front of active lava flows. These new images may help explain why Prometheus has been so faithfully active.</p><p>North is to the top of the picture, and the Sun illuminates the surface from almost directly behind the spacecraft. This illumination is good for imaging color variations, but poor for imaging topographic shading. However, some topography is visible here due to the combination of relatively high resolution (1.3 kilometers or 0.8 miles per picture element) and rugged areas over parts of Io. The image is centered at 2 degrees south latitude and 154 degrees west longitude. The images were taken at a distance of about 130,000 kilometers (81,000 miles) by Galileo's camera and have a resolution of 1.3 kilometers or 0.8 miles per picture element.</p><a href="/figures/prometheus_full.jpg"></a>Click on this image to view <br> a context image of Io's <br> volcano Prometheus.<br>(MRPS95334)<a href="/figures/io_traj_full.jpg"></a>Click on this image to view <br> Galileo's flight plan for I24 & I25.<br>(MRPS95336)<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 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://www2.jpl.nasa.gov/galileo/sepo/" target="_blank">http://www.jpl.nasa.gov/galileo/sepo</a><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02505" onclick="window.open(this.href); return false;" title="Voir l'image PIA02505: Close-up of Prometheus, Io (color) sur le site de la NASA">Voir l'image PIA02505: Close-up of Prometheus, Io (color) sur le site de la NASA.</a></div>
PIA02505: Close-up of Prometheus, Io (color)
<h1>PIA02506: Amirani-Maui: Longest Known Active Lava Flow in the Solar System</h1><div class="PIA02506" lang="en" style="width:336px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>This pair of volcanic features on Jupiter's moon Io represents the longest active lava flow known to exist in our solar system. This image, one of the highest resolution pictures ever taken of Io, was obtained by NASA s Galileo spacecraft on July 3, 1999. That was during Galileo's closest pass by Io since it entered orbit around Jupiter in December 1995.</p><p>The volcanic features, Amirani (right side of image) and Maui (to the left, just below the center of the image), were originally thought to be two separate volcanoes. However, Galileo images have shown that Maui is actually the active front of a lava flow that has extended westward from a vent at Amirani for more than 250 kilometers (160 miles). Observations by Galileo's near-infrared mapping spectrometer show a hotspot at Maui, so the lava must still be flowing. Other flows extend northward from the Amirani vent.</p><p>White plume deposits encircle the Amirani vent and are likely to be sulfur dioxide-rich vapors that have escaped at the vent, frozen and then snowed out onto the ground. The red deposits from the dark spot southwest of the Amirani vent appear to have been blown away from the stronger Amirani plume. The red material may be produced by a form of sulfur.</p><p>Amirani-Maui is more than 250 kilometers (160 miles) long. Such gigantic lava flows are found on Venus, the Earth, the Moon, and Mars. Massive eruptions on the Earth coincide with the times of major extinction events.</p><p>The image, in false color, uses the near-infrared, green and violet filters (slightly more than the visible range) of the spacecraft's camera, processed to enhance subtle color variations. North is to the top of the picture, and the Sun illuminates the surface from almost directly behind the spacecraft. This illumination is good for imaging color variations, but poor for imaging topographic shading. The image is centered at 23 degrees north latitude and 118 degrees west longitude. The images were taken at a distance of about 130,000 kilometers (81,000 miles) by Galileo's onboard solid state imaging camera and have a resolution of 1.3 kilometers or 0.8 miles per picture element.</p><a href="/figures/amirani_full.jpg"></a>Click on this image to view <br> a context image of Io's <br> volcano Amirani.<br>(MRPS95335)<a href="/figures/io_traj_full.jpg"></a>Click on this image to view <br> Galileo's flight plan for I24 & I25.<br>(MRPS95336)<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 Caltech.</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://www2.jpl.nasa.gov/galileo/sepo/" target="_blank">http://www.jpl.nasa.gov/galileo/sepo</a>."><a href="http://www2.jpl.nasa.gov/galileo/sepo/" target="_blank">http://www.jpl.nasa.gov/galileo/sepo</a>.</a></p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02506" onclick="window.open(this.href); return false;" title="Voir l'image PIA02506: Amirani-Maui: Longest Known Active Lava Flow in the Solar System sur le site de la NASA">Voir l'image PIA02506: Amirani-Maui: Longest Known Active Lava Flow in the Solar System sur le site de la NASA.</a></div>
PIA02506: Amirani-Maui: Longest Known Active Lava Flow in the Solar System
<h1>PIA02507: Highest Resolution Image Ever Obtained of Io</h1><div class="PIA02507" lang="en" style="width:797px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>Click on this image for a full resolution context image (in tiff format) that corresponds to the caption below. Click <a href="/figures/i24pillan_cntxt_full.jpg">here</a> for a jpeg format image.</p><a href="/figures/i24pillan_cntxt.tif"></a><p>The highest resolution image ever of Jupiter's volcanic moon Io, (the black and white image at top), was taken by NASA's Galileo spacecraft on October 10, 1999, from an altitude of 617 kilometers (417 miles). It shows an area about 7.2 kilometers (4.5 miles) long and 2.2 kilometers (1.4 miles)wide. Features as small as 9 meters (30 feet) can be discerned, providing a resolution which is 50 times better the previous best, taken by the Voyager spacecraft in 1979.</p><p>The box drawn in the center image, a Galileo image of Io taken earlier in the mission, shows the area displayed in the new image at top. The three color images below show the volcanic region from a much higher altitude than the other images and follow a volcanic eruption observed by Galileo earlier in mission</p><p>This new image targeted lava flows that erupted from the volcano Pillan. A complex mix of smooth and rough areas can be seen with clusters of pits and domes, many of which are the size of houses. The volcanic features are similar to those found on Earth and Mars. However, this combination of different types of lava flows has not been seen before in such a small area, demonstrating the variety of volcanic processes that continue to change the surface of Io.</p><p>North is to the top of the pictures and the Sun illuminates the surface from the right. In the top and middle images the Sun is only a few degrees above the horizon, emphasizing topography. Galileo scientists estimate that the cliff on the left side of the image ranges from 3 to 10 meters (10 to 33 feet) high.</p><p>In 1997 Galileo caught Pillan in the process of erupting. The explosion blanketed an area 400 kilometers (250 miles) in diameter with ash as seen in the series of three color images at the bottom. These images show the changes that have occurred at Pillan over the last three years<a href="/catalog/PIA02501"> (previous release)</a>. Pillan is the new dark spot in middle color frame and the big, red ring seen in all three images is formed by the plume from the nearby volcano Pele. Galileo's camera and near-infrared mapping spectrometer measured the temperatures of the lavas during the eruption and found that they were hotter than any known eruption on Earth in the last two billion years.</p><p>The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC.</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 URL <a href="http://www.jpl.nasa.gov/galileo">http://www.jpl.nasa.gov/galileo</a>. Background information and educational context for the images can be found at URL<a href="http://www2.jpl.nasa.gov/galileo/sepo/" target="_blank">http://www.jpl.nasa.gov/galileo/sepo</a><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02507" onclick="window.open(this.href); return false;" title="Voir l'image PIA02507: Highest Resolution Image Ever Obtained of Io sur le site de la NASA">Voir l'image PIA02507: Highest Resolution Image Ever Obtained of Io sur le site de la NASA.</a></div>
PIA02507: Highest Resolution Image Ever Obtained of Io
<h1>PIA02508: Galileo discovers caldera at Prometheus Volcano, Io</h1><div class="PIA02508" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>This is a high-resolution image of part of Prometheus, an active volcano on Jupiter's volcanic moon Io. The image was taken by NASA's Galileo spacecraft on October 10, 1999, during its close flyby of Io. It shows a volcanic caldera, a large depression formed by the collapse of the ground after a volcanic eruption. Some terrestrial examples of calderas can be found in Hawaii. This image also shows dark lava flows and a strange, lumpy surface covered with sulfur-rich snow. The new image is shown over an earlier, color view.</p><p>In <a href="/catalog/PIA02505">earlier, lower resolution images</a>, it appeared that all the dark material at Prometheus comprised a single, long lava flow. The new image shows for the first time that the northeastern end of this dark feature is actually a lava-filled caldera 28 kilometers (17 miles) long and 14 kilometers (9 miles) wide. The underground source of the Prometheus lava is probably beneath this newly discovered caldera.</p><p>The lava flows that spill over the west rim of the newly discovered caldera clearly indicate that, at some point in time, the entire caldera was filled with lava. It is not clear whether the lava to the south of the caldera originally erupted within the caldera and flowed out, or if it erupted from a vent in the south and then flowed north into the caldera.</p><p>Galileo scientists are intrigued also by the snowfield containing hummocks, seen to the east of the Prometheus caldera. They are currently examining a number of alternative models for their formation. One idea is that the hummocks, or routed knolls, are the results of the supersonic blasts from Io's volcanoes plastering material onto one side of pre-existing lumps on the ground.</p><p>The black and white, high-resolution image was taken with a filter that let in only a part of the infrared spectrum close to the visible wavelengths. <a href="/catalog/PIA02509">The "color" of materials in the infrared is an important tool in determining the chemical composition of planetary surfaces</a>. North is to the top of the picture and the sun illuminates the surface from almost behind the spacecraft. The resolution is 120 meters (400 feet) per pixel element. This resolution is more than 10 times better than the previous best view of this region. The image covers an area about 96 kilometers (60 miles) wide and 29 kilometers (18 miles) high. It was taken at a distance of 12,000 kilometers (7,500 miles) from Io by the camera onboard Galileo.</p><p>The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC.</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://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://galileo.jpl.nasa.gov/images/images.html">http://galileo.jpl.nasa.gov/images/images.html</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02508" onclick="window.open(this.href); return false;" title="Voir l'image PIA02508: Galileo discovers caldera at Prometheus Volcano, Io sur le site de la NASA">Voir l'image PIA02508: Galileo discovers caldera at Prometheus Volcano, Io sur le site de la NASA.</a></div>
PIA02508: Galileo discovers caldera at Prometheus Volcano, Io
<h1>PIA02510: Pele's glow</h1><div class="PIA02510" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>Brightly glowing lava from the volcano Pele is seen in this image taken by NASA's Galileo spacecraft as it receded from its close flyby of Jupiter's moon Io in October, 1999. The image at left shows Io's surface in approximately true color, centered on the large red ring of sulfur that was deposited by Pele's plume and reaches more than 1,300 kilometers (808 miles) in diameter. A false color infrared composite of the same region is shown on the right. The dark red dot at the center of the ring (seen in the false color picture) is the glow of <a href="/catalog/PIA02511">hot lava at the heart of the volcano</a>. Temperatures up to 1,027 degrees Celsius (1,880 degrees fahrenheit) have been previously measured for Pele's lava. The glow is bright enough to be imaged in daylight, allowing scientists to precisely pinpoint the eruptive center.</p><p>The region imaged is centered on 18 degrees south, 255 degrees west, and is almost 2,000 kilometers (1,243 miles) across. North is toward the top right of the picture and the sun illuminates the surface from the west.</p><p>Launched in October 1989, Galileo entered orbit around Jupiter on December 7, 1995. The spacecraft's mission is to conduct detailed studies of the giant planet, its largest moons and the Jovian magnetic environment. 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/" 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/PIA02510" onclick="window.open(this.href); return false;" title="Voir l'image PIA02510: Pele's glow sur le site de la NASA">Voir l'image PIA02510: Pele's glow sur le site de la NASA.</a></div>
PIA02510: Pele's glow
<h1>PIA02511: Pele's Hot Caldera Margin</h1><div class="PIA02511" lang="en" style="width:682px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>The volcano Pele glows in the night in this close-up image of Jupiter's moon Io, obtained by NASA's Galileo spacecraft in the closest-ever Io flyby on October 10, 1999. Only surfaces hotter than 600 degrees Celsius (1,100 degrees Fahrenheit) are visible in this image. The hot material forms a thin, curving line more than 10 kilometers (6 miles) long and up to 50 meters (150 feet) wide. Galileo scientists believe that the changes in brightness along the curving line are due to variations in the amount of hot lava exposed at the surface. Data acquired previously suggest that the liquid lava at Pele is over 1,200 degrees Celsius (2,200 degrees Fahrenheit). Such lava would cool and become invisible in this image in just a few minutes. Therefore, this image outlines parts of the volcano that are at most a few minutes old.</p><p>The outline of the fresh, hot material is superimposed on the best daytime image of Pele (bottom), showing that the hot material follows the margin of Pele's caldera. A caldera is a depression caused by collapse during a volcanic eruption. Galileo scientists hypothesize that the Pele caldera is filled with liquid lava, with the floating crust broken-up along the margins where it hits the cliffs along the caldera's walls. The lava lake is probably confined to the dark, southern part of the Pele caldera, which covers an area of about 15 by 10 kilometers (10 by 6 miles). Previous data collected by Galileo indicate that hot material covers only an area of about 800 by 800 meters (0.5 by 0.5 miles). This suggests that most of the lava lake is covered by a cooler crust that floats on top of the molten lava. The behavior of this lava lake is similar to that of Hawaiian lava lakes, although Pele covers an area several thousand times larger than the lakes in Hawaii. Interestingly, the image of Pele's caldera obtained by Galileo in October shows only about one-percent of the<a href="/catalog/PIA02510">hot area was known to be on the volcano</a>. This indicates that 99-percent of the activity at Pele is in a region that was not imaged in this flyby.</p><a href="/figures/PuuOo1.jpg"></a><br>Pu'u O'o lava lake, Hawaii, 1992<p>North is to the top of the picture and the sun is on the other side of Io. It is centered at 18.6 degrees south latitude and 255.7 degrees west longitude, looking obliquely at an area approximately 10 kilometers (6 miles) by 10 kilometers (6 miles) in size. The picture has a resolution of 30 meters (100 feet) per picture element and is taken in the clear filter using a 45.8 millisecond exposure time. The images were taken by the camera onboard Galileo from a range of about 1,400 kilometers (840 miles).</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/" 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/PIA02511" onclick="window.open(this.href); return false;" title="Voir l'image PIA02511: Pele's Hot Caldera Margin sur le site de la NASA">Voir l'image PIA02511: Pele's Hot Caldera Margin sur le site de la NASA.</a></div>
PIA02511: Pele's Hot Caldera Margin
<h1>PIA02512: Ongoing Geologic Activity at Prometheus Volcano, Io</h1><div class="PIA02512" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>This collage of images shows the dizzying rate of geologic activity at one of the many erupting volcanoes on Jupiter's moon Io, as viewed by NASA's Galileo spacecraft during the closest-ever Io flyby on October 10, 1999. The top panel shows the best overall view of the Prometheus volcano, combining a picture at a resolution of 120 meters (400 feet) per picture element with a picture at a resolution of 1.5 kilometers (about one mile) per picture element. Inset within this panel is a smaller copy of the mosaic with a temperature map superimposed.</p><p>The Galileo camera took the pictures, while the temperatures were measured by the spacecraft's near infrared mapping spectrometer instrument. Combining these data, Galileo scientists have created a description of the eruption at Prometheus. The magma is stored in an underground chamber beneath the caldera (dark, bean-shaped feature) at the northeastern end of Prometheus (top right). The lava reaches the surface about 15 kilometers(10 miles) south of the caldera. This point is marked by the blue, eastern hot spot in the temperature map and by a streak of red, sulfur-rich material (see color panel on the lower left). From the volcanic vent, the lava travels almost 100 kilometers (60 miles) through lava tubes to the front of the flow. The exposed liquid lava produces the large high temperature area on the western end of Prometheus (color panel at lower left). A 100 kilometer(60 mile) tall plume of sulfur-dioxide rich gas also rises above these active lava flows. A smaller breakout of liquid lava midway along the tube forms a faint (purple) hot spot.</p><p>Scientists at the University of Arizona, compared the pictures taken on <a href="/catalog/PIA02505">July 3rd</a> and October 10th of this year. They found that changes (see middle and right lower panels) have occurred in the intervening 3 months. A breakout from the middle of the lava tube appears to have taken place within this three-month period, spreading a new dark deposit to the north of the older lava flows. It also appears that the gas discharge from the volcanic vent at the eastern end of the flow has increased. There is a new fan of dark material streaming out from this location. Furthermore, the new, bright crescent-shaped deposit across the middle of Prometheus suggests that the main (western) plume has been pushed aside by the increased gas release to the east.</p><a href="/figures/promsimplemap.jpg"></a><br>Map of Prometheus<p>North is to the top in all images and the sun is illuminating the surface from slightly to the left of overhead. All the images are centered at 2 degrees south and 154 degrees west. The top image has a resolution of 1.5 kilometers (about one mile) per picture element and the high-resolution inset has a resolution of 120 meters (390 feet). The color image at the bottom has a resolution of 2.6 kilometers (1.6 miles) per picture element. The two black and white image at the bottom have resolutions of 1.5 kilometers (about one mile) per picture element.</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/PIA02512" onclick="window.open(this.href); return false;" title="Voir l'image PIA02512: Ongoing Geologic Activity at Prometheus Volcano, Io sur le site de la NASA">Voir l'image PIA02512: Ongoing Geologic Activity at Prometheus Volcano, Io sur le site de la NASA.</a></div>
PIA02512: Ongoing Geologic Activity at Prometheus Volcano, Io
<h1>PIA02513: Collapsing Mountains on Io</h1><div class="PIA02513" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>Unusual mountains on Jupiter's moon Io are shown in these images that were captured by NASA's Galileo spacecraft during its close Io flyby on October 10, 1999. The top four pictures show four different mountains at resolutions of about 500 meters (1,600 feet) per picture element. The bottom picture is a closeup of another mountain. It is also one of the highest resolution images ever obtained of Io, with a resolution of 9 meters (30 feet) per picture element. The lower resolution images show a range of mountain structures from angular peaks on the left to gentler plateaus, surrounded by very gently sloping debris aprons on the right.</p><p>Galileo scientists believe that these images illustrate the deterioration of Ionian mountains. If this is the case, it means that the more angular mountains on the left are younger than the rounded mountains on the right. Almost all of the mountains exhibit ridges parallel to their margins. These ridges indicate material is moving down the sides of the mountains due to gravity. The ridges are similar to structures observed at the base of Olympus Mons on Mars, so comparative studies may help us understand surface processes on both planets. The very high-resolution image shows a closeup of a degraded mountain. This image (which is strikingly different from <a href="/catalog/PIA02507">the other image of comparable resolution which targeted recent lava flows</a>) shows a lumpy landscape. Curiously, the variation in brightness between the dark and light areas within this image is the greatest seen to date on Io. Galileo scientists are continuing to investigate the processes that produce this puzzling surface.</p><p>The Sun illuminates the surface from the left in all five images. North is to the top in the top four images. In order to keep the Sun angle consistent in all of the images, north is to the bottom in the bottom image. The upper left image is centered at 18.7 degrees north latitude, 81.4 degrees west longitude, and covers a region 175 kilometers (108 miles) by 170 kilometers (106 miles). The lower left image is centered at about one degree north latitude and 81.7 degrees west longitude and covers a region 135 kilometers (84 miles) by 200 kilometers (124 miles). The middle image is centered at 25.6 degrees north latitude, 96.7 degrees west longitude and covers a region 130 kilometers (81 miles) by 275 kilometers(170 miles). The right image is centered at 14.4 degrees north latitude, 104.7 degrees west longitude and covers a region 125 kilometers (78 miles) by 205 kilometers (130 miles). The bottom image is centered at 4 degrees north latitude and 214.6 degrees west longitude and was taken at a range of 882 kilometers (548 miles).</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/" 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/PIA02513" onclick="window.open(this.href); return false;" title="Voir l'image PIA02513: Collapsing Mountains on Io sur le site de la NASA">Voir l'image PIA02513: Collapsing Mountains on Io sur le site de la NASA.</a></div>
PIA02513: Collapsing Mountains on Io
<h1>PIA02517: Reconstruction of Scrambled Io Images</h1><div class="PIA02517" 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 depicts the magic worked by JPL engineers to repair radiation damage to images taken by NASA's Galileo spacecraft camera during an October 10 close flyby of Jupiter's volcanic moon Io.</p><p>The majority of the Io images acquired by Galileo that day were taken in a camera mode in which 2x2 blocks of picture elements are supposed to be added together during readout of the image from the detector. Because the environment around Io has very high radiation, this mode was implemented to provide additional protection against corruption of the images due to radiation-induced noise. However, apparently due to accumulated radiation damage to the camera electronics, this readout mode did not function properly during the flyby. The effect was that the right and left sides of the images were added together during readout, rather than adjacent pairs of picture elements. This produced something akin to a double-exposed image.</p><p>Engineers figured out how the images had been garbled by carefully examining the images and the way the detector readout is commanded. Until recently, it was thought that repair of the images would be impossible. However, an innovative technique has just been developed at JPL for separating the two halves without introducing excessive errors. The scrambled raw data were unscrambled by a program developed using the LabVIEW software from National Instruments of Austin, TX. The image recovery results have been amazing. They allow for reliable analysis of the surface morphologies seen in the Io images.</p><p>The image shown here (left: -- original scrambled image; right -reconstructed image) covers a portion of the lava flows emanating from a<a href="/catalog/PIA02504">volcanic center on Io named Zamama</a>. The intricate, convoluted margins of the flows are characteristic of "pahoehoe" (smooth, ropy) lava flows seen on Earth, and provide information on how the lava erupted and advanced over the ground.</p><p>North is to the lower left of the picture and the Sun illuminates the surface from the lower left. The image, centered at 17.7 degrees latitude and 172.2 degrees longitude, covers an area approximately 16 by 16 kilometers (10 by 10 miles). The finest details that can be discerned in this picture are about 80 meters (260 feet) across. The image was taken on October 10, 1999 at a range of 1,800 kilometers (1,100 miles) by Galileo's onboard camera.</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 in Pasadena. This image and other images and data received from Galileo are posted 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/PIA02517" onclick="window.open(this.href); return false;" title="Voir l'image PIA02517: Reconstruction of Scrambled Io Images sur le site de la NASA">Voir l'image PIA02517: Reconstruction of Scrambled Io Images sur le site de la NASA.</a></div>
PIA02517: Reconstruction of Scrambled Io Images
<h1>PIA02518: Bright Channelized Lava Flows on Io</h1><div class="PIA02518" lang="en" style="width:797px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>This image of Jupiter's moon Io, taken by NASA's Galileo spacecraft on November 25, 1999, shows a bright lava flow with a distinct dark channel in the middle. This type of winding channel is a common sight on shallow slopes in lava flows on Earth that are moving fairly quickly. The serrated margins are characteristic of fluid lava that is able to work its way into every available nook and crevice. What is unusual about this lava flow is its bright color -- most lava flows on Io and the other planets are dark. This leads Galileo scientists to speculate that these lava flows are composed of sulfur, rather than silicate rock. The lava flow appears to emanate from a caldera named Emakong, which is just beyond the left edge of the picture.</p><p>North is to the upper left of the picture and the Sun illuminates the surface from almost behind the spacecraft. The image, centered at -3.7degrees latitude and 117.4 degrees longitude, covers an area approximately 120 by 40 kilometers (75 by 25 miles). The resolution is 150 meters (500 feet) per picture element. The image was taken at a range of 15,000 kilometers (9,400 miles) by the camera onboard Galileo.</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 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/PIA02518" onclick="window.open(this.href); return false;" title="Voir l'image PIA02518: Bright Channelized Lava Flows on Io sur le site de la NASA">Voir l'image PIA02518: Bright Channelized Lava Flows on Io sur le site de la NASA.</a></div>
PIA02518: Bright Channelized Lava Flows on Io
<h1>PIA02519: Lava Fountains on Io</h1><div class="PIA02519" 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 collected by NASA's Galileo spacecraft on Thanksgiving Day, November 25,1999 shows a fountain of lava spewing above the surface of Jupiter's moon Io. The active lava was hot enough to cause what the camera team describes as "bleeding" in Galileo's camera, caused when the camera's detector is so overloaded by the brightness of the target that electrons spill down across the detector. This shows up as a white blur in the image.</p><p>Most of the hot material is distributed along a wavy line which is interpreted to be hot lava shooting more than 1.5 kilometers (1-mile) high out of a long crack, or fissure, on the surface. There also appear to be additional hot areas below this line, suggesting that hot lava is <a href="/catalog/PIA02525">flowing away from the fissure</a>. Initial estimates of the <a href="/catalog/PIA02521">lava temperature</a> indicate that it is well above 1,000 Kelvin (1,300 Fahrenheit) and might even be hotter than 1,600 Kelvin (2,400 Fahrenheit).</p><p>These images were targeted to provide the first close-up view of a chain of huge calderas (large volcanic collapse pits). These calderas are some of the largest on Io and they dwarf other calderas across the solar system. At 290 by 100 kilometers (180 by 60 miles), this chain of calderas covers an area seven times larger than the largest caldera on the Earth. The new images show the complex nature of this giant caldera on Io, with smaller collapses occurring within the elongated caldera.</p><p>Also of great interest is the flat-topped mesa on the right. The scalloped margins are typical of a process geologists call "sapping," which occurs when erosion is caused by a fluid escaping from the base of a cliff. On Earth, such sapping features are caused by springs of groundwater. Similar features on Mars are one of the key pieces of evidence for past water on the Martian surface. However, on Io, the liquid is presumed to be pressurized sulfur dioxide. The liquid sulfur dioxide should change to a gas almost instantaneously upon reaching the near-vacuum of Io's surface, blasting away material at the base of the cliff. The sulfur dioxide gas eventually freezes out on the surface of Io in the form of a frost. As the frost is buried by later deposits, it can be heated and pressurized until it becomes a liquid. This liquid then flows out of the ground, completing Io's version of the "water cycle."</p><p>North is to the upper left of the picture and the Sun illuminates the surface from the lower left. The image, centered at 61.1 degrees latitude and 119.4 degrees longitude, covers an area approximately 300 by 75 kilometers (190-by-47 miles). The resolution is 185 meters (610 feet) per picture element. The image was taken at a range of 17,000 kilometers(11,000 miles) by Galileo's onboard camera.<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/PIA02519" onclick="window.open(this.href); return false;" title="Voir l'image PIA02519: Lava Fountains on Io sur le site de la NASA">Voir l'image PIA02519: Lava Fountains on Io sur le site de la NASA.</a></div>
PIA02519: Lava Fountains on Io
<h1>PIA02520: Mountains on Io</h1><div class="PIA02520" lang="en" style="width:797px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>This image taken by NASA's Galileo spacecraft during its close flyby of Jupiter's moon Io on November 25, 1999 shows some of the curious mountains found there. The Sun is illuminating the scene from the left, and because it is setting, the Sun exaggerates the shadows cast by the mountains. By measuring the lengths of these shadows, Galileo scientists can estimate the height of the mountains. The mountain just left of the middle of the picture is 4 kilometers (13,000 feet) high and the small peak to the lower left is 1.6 kilometers (5,000 feet) high.</p><p>These mountains, like <a href="/catalog/PIA02513">others imaged during a previous Galileo flyby of Io in October</a>, seem to be in the process of collapsing. Huge landslides have left piles of debris at the bases of the mountains. The ridges that parallel their margins are also indicative of material moving down the mountainsides due to gravity.</p><p>North is to the upper left of the picture. The image, centered at -8.1degrees latitude and 78.7 degrees longitude, covers an area approximately 210-by-110 kilometers (130-by-70 miles). The resolution is 267 meters (880 feet) per picture element. The image was taken at a range of 25,000 kilometers (16,000 miles) by Galileo's onboard camera.</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/PIA02520" onclick="window.open(this.href); return false;" title="Voir l'image PIA02520: Mountains on Io sur le site de la NASA">Voir l'image PIA02520: Mountains on Io sur le site de la NASA.</a></div>
PIA02520: Mountains on Io
<h1>PIA02522: Earth-Based Observations of a Fire Fountain on Io</h1><div class="PIA02522" lang="en" style="width:688px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>This false-color infrared image of the Sunlit disk of Jupiter's moon Io was taken at the NASA Infrared Telescope Facility at Mauna Kea, Hawaii, a few hours after a November 25, 1999 close Io flyby by NASA's Galileo spacecraft. The bright spot at the 1 o'clock position is the same lava fountain seen close-up by Galileo's camera, but in this case it is seen from Earth at a distance of 630 million kilometers (390 million miles).</p><p>When this image was taken, the fiery lava fountain was almost on the edge of Io's disk and about to disappear from view due to Io's rotation. The lava fountain was seen from an angle just 5.5 degrees above horizontal. Its prominence when seen so obliquely confirms that this eruption is indeed composed of fiery fountains rising up above the surface; horizontal lava flows would be much harder to see from so close to the horizontal.</p><p>Astronomers making Earth-based telescopic observations see a bright spot like this one somewhere on Io only about 20 percent of the time, so the Galileo team was fortunate to catch one in its narrow field of view. Astronomer John Spencer, who has watched this type of eruption for many years on Io from Mauna Kea, said, "We thought that some of these eruptions might be due to lava fountains, but it's incredible to see that idea confirmed so spectacularly by Galileo."</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/PIA02522" onclick="window.open(this.href); return false;" title="Voir l'image PIA02522: Earth-Based Observations of a Fire Fountain on Io sur le site de la NASA">Voir l'image PIA02522: Earth-Based Observations of a Fire Fountain on Io sur le site de la NASA.</a></div>
PIA02522: Earth-Based Observations of a Fire Fountain on Io
<h1>PIA02523: Earth-based images of the Fall 1999 Loki Eruption</h1><div class="PIA02523" lang="en" style="width:630px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>These false-color images of Io and Jupiter were taken with the NASA Infrared Telescope Facility at Mauna Kea, Hawaii, as part of a campaign to support closeup Io observations by NASA's Galileo spacecraft. These and other Earth-based observations show that Io's most powerful volcano, Loki, began one of its periodic major eruptions about a month before Galileo's October Io flyby, and that the eruption was continuing during the Galileo flyby. These infrared images (taken at a wavelength of 3.8 microns) show Sunlight reflected from the edge of Jupiter's disk on the left-hand side, and the heat from several glowing volcanoes on Io on the right. Io is in Jupiter's shadow, so no Sunlight falls on it -- the volcanoes are all we see.</p><p>On August 9, 1999 (left), several volcanoes glowed faintly with roughly equal brightness. However, on October 10, 1999, roughly 20 hours before Galileo flew past, a single volcano, Loki, dominated the image. Loki brightened by a factor of ten in the period between these images. Other observations from the NASA Infrared Telescope and from Wyoming Infrared Telescope near Laramie operated by the University of Wyoming show that most of this brightening occurred during September.</p><p>Earth-based observations since the 1980s have shown that these periodic bright eruptions are typical behavior for Loki. They occur about once per year and last several months. Galileo has given us our first chance to see one of these eruptions up close.</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/PIA02523" onclick="window.open(this.href); return false;" title="Voir l'image PIA02523: Earth-based images of the Fall 1999 Loki Eruption sur le site de la NASA">Voir l'image PIA02523: Earth-based images of the Fall 1999 Loki Eruption sur le site de la NASA.</a></div>
PIA02523: Earth-based images of the Fall 1999 Loki Eruption
<h1>PIA02526: Ionian Mountains and Calderas, in Color</h1><div class="PIA02526" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>This picture of Jupiter's volcanic moon Io combines high-resolution black and white images taken by NASA's Galileo spacecraft on October 10, 1999, with lower resolution color images taken by Galileo on July 3, 1999 to help scientists better understand the relationships between the different surface materials and the underlying geologic structures. For example, there is red material, which is often associated with areas where lava is erupting onto the surface and is thought to be a compound of sulfur, around the margin of Monan Patera (the elongated caldera just to the lower right of center). The broad circle of bright, white material (just to the left of center) is thought to be sulfur-dioxide which is being deposited from the plume Amirani.</p><p>The lengths of the shadows cast by the mountains make it possible to estimate the mountains¹ heights. The southern mountain on the far right of the mosaic is approximately 8 kilometers (26,000 feet) high and the mountain to the north of it is approximately 4 kilometers (13,000 feet) high.</p><p>North is to the top and the image is centered at 22.8 degrees north latitude and 109.5 degrees west longitude. The higher resolution images have a sharpness of about 500 meters (or yards) per picture element and they are illuminated from the left. These images were taken at a range of 25,000 kilometers (15,500 miles). The color images are illuminated from almost directly behind the spacecraft. The color images were taken at a distance of about 130,000 kilometers (81,000 miles) and show a resolution of 1.3 kilometers (0.8 miles) 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 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/PIA02526" onclick="window.open(this.href); return false;" title="Voir l'image PIA02526: Ionian Mountains and Calderas, in Color sur le site de la NASA">Voir l'image PIA02526: Ionian Mountains and Calderas, in Color sur le site de la NASA.</a></div>
PIA02526: Ionian Mountains and Calderas, in Color
<h1>PIA02527: Zal Patera, Io, in color</h1><div class="PIA02527" lang="en" style="width:712px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>The Zal Patera region of Jupiter's volcanic moon Io is shown in this combination of high-resolution black and white images taken by NASA's Galileo spacecraft on November 25, 1999 and lower resolution color images taken by Galileo on July 3, 1999. By combining both types of images, Galileo scientists can better understand the relationships between the different surface materials and the underlying geologic structures. For example, in the center toward the top of the picture, the edge of the caldera, or volcanic crater, is marked by the black flows, and it coincides with the edge of a plateau. Also, the red material (just above and to the right of the center of the image) is typically associated with regions where lava is erupting onto the surface. Here the red material follows the base of a mountain, which may indicate that sulfurous gases are escaping along a fault associated with the formation of the mountain.</p><p>Scientists can use the lengths of the shadows cast to estimate the height of the mountains. They estimate that the northernmost plateau, which bounds the western edge of Zal Patera, rises up to approximately 2 kilometers (6,600 feet) high. The mountain to the south of the caldera has peaks up to approximately 4.6 kilometers (15,000 feet) high, while the small peak at the bottom of the picture is approximately 4.2 kilometers (14,000 feet) high.</p><p>North is to the top of the image, which is centered at 33.7 degrees north latitude and 81.9 degrees west longitude. The higher resolution images have a sharpness of about 260 meters (or yards) per picture element, and they are illuminated from the left. These images were taken on November 25, 1999 at a range of 26,000 kilometers (16,000 miles). The color images are illuminated from almost directly behind the Galileo spacecraft. The resolution of the color images is 1.3 kilometers (0.8 miles) per picture element. They were taken on July 3, 1999 at a distance of about 130,000 kilometers (81,000 miles).</p><p>The Jet Propulsion Laboratory, Pasadena, CA manages Galileo 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>.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02527" onclick="window.open(this.href); return false;" title="Voir l'image PIA02527: Zal Patera, Io, in color sur le site de la NASA">Voir l'image PIA02527: Zal Patera, Io, in color sur le site de la NASA.</a></div>
PIA02527: Zal Patera, Io, in color
<h1>PIA02534: Terrain near Io's south pole, in color</h1><div class="PIA02534" lang="en" style="width:769px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>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.</p><p>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.</p><p>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.</p><p>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).</p><p>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.</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/PIA02534" onclick="window.open(this.href); return false;" title="Voir l'image PIA02534: Terrain near Io's south pole, in color sur le site de la NASA">Voir l'image PIA02534: Terrain near Io's south pole, in color sur le site de la NASA.</a></div>
PIA02534: Terrain near Io's south pole, in color
<h1>PIA02535: Culann Patera, Io, in false color</h1><div class="PIA02535" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>Culann Patera, one of the most colorful volcanic centers on Io, is the centerpiece of this mosaic of the best high-resolution, color view of Io yet returned by NASA's Galileo spacecraft. The picture was constructed from images taken through the red, green, and violet filters of Galileo camera and has been processed to enhance the color variations. The resolution is about 200 meters (or yards) per picture element, and north is to the top.</p><p>The color mosaic shows the complex relationships between the diffuse red deposit, the more confined green deposit, and the various colored lava flows. Culanns central caldera (above and to the right of center) has a highly irregular, scalloped margin and a green-colored floor. Lava flows spill out of the caldera on all sides. A dark red, curving line extending northwest from the southwestern tip of the caldera may mark a crusted-over lava tube feeding the dark (and hot) silicate flows to the northwest. Unusual dark red flows to the southeast of the caldera may be sulfur flows or silicate flows whose surfaces have been modified. The diffuse red material around the caldera is believed to be a compound of sulfur deposited from a plume of gas.</p><p>Culanns caldera and several lava flows extending from the caldera are coated by greenish materials. Green material can also be seen in the caldera to the lower right of the image, named Tohil Patera. The greenish material often has sharp boundaries, so it is apparently confined to the caldera floor and the dark flows. Galileo scientists are investigating whether the greenish material forms as a coating of sulfur-rich material on warm silicate lavas.</p><p>The images were taken on November 25, 1999 during Galileo's 25th orbit at a distance of 20,000 kilometers (12,500 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.</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/PIA02535" onclick="window.open(this.href); return false;" title="Voir l'image PIA02535: Culann Patera, Io, in false color sur le site de la NASA">Voir l'image PIA02535: Culann Patera, Io, in false color sur le site de la NASA.</a></div>
PIA02535: Culann Patera, Io, in false color
<h1>PIA02536: 1997 Lava Flows Near Pillan Patera, Io</h1><div class="PIA02536" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>This very high resolution (19 meters, or about 21 yards, per picture element) mosaic shows the complex collection of lava flows, pits, domes, and possibly rafted plates of lava on Io. The images were taken by NASA's Galileo spacecraft on October 11, 1999 during its 24th orbit. The observation targeted a 70-kilometer (44-mile) long lava flow that erupted from Pillan Patera in June 1997. Rafted plates like those that appear in this image are also seen on Earth and Mars; they may indicate that the lava was flowing rapidly enough to rip apart the crust as it formed. Galileo scientists believe that most of these lava flows, which cover about 400square kilometers (160 square miles), were emplaced in about two weeks. A shadow that appears to be cast by the edge of an individual lava flow (lower left) indicates that the flow is 10 meters, or yards, thick.</p><p>The pits and domes, which range from a few tens of meters to many hundreds of meters in scale, are more difficult to explain. One possibility is that these are the result of interactions between the hot lava and Io's volatile-rich surface. Such vents are observed on Earth when lava flows interact with ground water or ice far from the actual source of the lava.</p><p>A joint observation of Pillan on June 27, 1996 by Galileo's onboard camera and near-infrared mapping spectrometer provided a temperature estimate forth lava of 1,900 Kelvins (3,900 degrees Fahrenheit), hundreds of degrees hotter than terrestrial eruptions. Although the lava flows have cooled significantly since then, they were still warm at the time of these observations.</p><p>North is to the top of the picture and the Sun illuminates the surface from the right. The images were taken on October 11, 1999 at a distance of 1,900 kilometers (1,200 miles) from Io. The large doses of radiation to which the spacecraft is subjected each time it passes close to Jupiter caused a problem with Galileo's camera, which resulted in scrambling of these images. Engineers at NASA's Jet Propulsion Laboratory, Pasadena, CA, were able to reconstruct the images, but black stripes remain where some data could not be recovered.</p><p>JPL manages the mission for NASA's Office of Space Science, Washington, D.C. 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>.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02536" onclick="window.open(this.href); return false;" title="Voir l'image PIA02536: 1997 Lava Flows Near Pillan Patera, Io sur le site de la NASA">Voir l'image PIA02536: 1997 Lava Flows Near Pillan Patera, Io sur le site de la NASA.</a></div>
PIA02536: 1997 Lava Flows Near Pillan Patera, Io
<h1>PIA02537: Lava Flows at Zamama, Io</h1><div class="PIA02537" 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 shows a portion of a long lava flow that appeared during the 17 years between flybys of Io by NASA's Voyager and Galileo spacecraft. The images are high resolution (35-40 meters, or 38-44 yards per picture element), and were acquired by Galileo on October 11, 1999during its 24th orbit. The lava flow is 100 kilometers (60 miles) long.</p><p>The dark flows have intricate margins that are characteristic of a type of lava flow seen on Earth called pahoehoe. The source of the lava flows is a 25-kilometer (16-mile) long fissure that extends to the east of the central vent off the mosaic to the upper left. Some of the lava flows at the western end of the mosaic have channels with bright floors. These channels may have been carved by sulfur lava flows, or they may have been carved by silicate lava flows which were later covered by bright material.</p><p>North is to the top of the mosaic. The images were taken at a distance of 3,500 to 4,000 kilometers (2,200 to 2,500 miles) from Io. The large doses of radiation to which the spacecraft is subjected each time it passes close to Jupiter caused a problem with Galileo's camera, which resulted in scrambling of these images. Engineers at NASA's Jet Propulsion Laboratory, Pasadena, CA, were able to reconstruct the images, but black stripes remain where some data could not be recovered. The streaks from lower left to upper right are artifacts from the reconstruction.</p><p>JPL manages the mission for NASA's Office of Space Science, Washington, D.C. 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/PIA02537" onclick="window.open(this.href); return false;" title="Voir l'image PIA02537: Lava Flows at Zamama, Io sur le site de la NASA">Voir l'image PIA02537: Lava Flows at Zamama, Io sur le site de la NASA.</a></div>
PIA02537: Lava Flows at Zamama, Io
<h1>PIA02538: Changes Observed in Just 4.5 Months at Prometheus, Io</h1><div class="PIA02538" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>These images illustrate just how quickly the surface of Io is changing. The image on the left shows lava flows from the volcano Prometheus as seen by NASA's Galileo spacecraft on October 11, 1999 on its 24th orbit (I24). White streaks emanating from around the edge of the flow may be frost deposited by small plumes of gas rich in sulfur dioxide that is vaporized by the hot lava. Bright material from the Prometheus plume quickly covers any cool surface; therefore, the darkest areas are the youngest lava flows. The middle image shows the same area as it appeared to Galileo 4-1/2 months later, on February 22, 2000 during its 27th orbit (I27). Numerous changes in the shapes and locations of the dark lava flows and bright streaks are evident.</p><p>The image on the right is a ratio of the I27 and I24 images (constructed by dividing the I27 image by the I24 image) which illustrates the changes that occurred between I24 and I27. Anything that became darker between October and February is dark in the ratio image and anything that became brighter is bright in the ratio. The juxtaposition of the dark and bright areas in the ratio image indicates that most of the fresh (dark) flows seen in I27 are extensions of the flows that were fresh (dark) during I24. Approximately 60 square kilometers (23 square miles) were covered by new lava flows in the 134 days between the two images. This means the average rate at which lava is covering the surface is about .45 square kilometers(.18 square miles) per day. This rate for Prometheus is about 10 times higher than peak eruption rates at Kilauea in Hawaii.</p><p>North is to the top in all images, and the images have resolutions of about 180 meters (or yards) per picture element. The large doses of radiation to which the spacecraft is subjected each time it passes close to Jupiter caused a problem with Galileo's camera, which resulted in scrambling of the I24 image. Engineers at NASA's Jet Propulsion Laboratory (JPL), Pasadena, CA, were able to reconstruct the image, but a black stripe remains where data could not be recovered. Some areas that could not be reconstructed appear blurred. To avoid a recurrence of this problem, a different camera mode was used during I27, so the later image is fine.</p><p>JPL 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/PIA02538" onclick="window.open(this.href); return false;" title="Voir l'image PIA02538: Changes Observed in Just 4.5 Months at Prometheus, Io sur le site de la NASA">Voir l'image PIA02538: Changes Observed in Just 4.5 Months at Prometheus, Io sur le site de la NASA.</a></div>
PIA02538: Changes Observed in Just 4.5 Months at Prometheus, Io
<h1>PIA02539: Bright Lava Flows at Emakong Patera, Io</h1><div class="PIA02539" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>NASA's Galileo spacecraft observed this volcano, Emakong Patera, a large, dark caldera from which numerous bright flows extend out in all directions, on November 25, 1999. Unlike many of the other volcanoes on Io, high-temperature material has never been observed at Emakong. These high-resolution (150 meters, or 164 yards, per picture element) images revealing the intricate nature of the lava flows were taken during Galileo's 25th orbit.</p><p>A bright flow emanates to the southeast of the caldera and spreads eastward. A dark channel runs through the flow and may have fed it as it grew. The margins of this bright flow are convoluted, indicating that the lava was able to move through narrow topographic constrictions, or that inexperienced numerous small breakouts. These observations are consistent with a low-viscosity liquid. A contender for the composition of this bright, low-viscosity lava is sulfur. While Galileo has frequently detected high-temperature silicate lava flows, sulfur flows may also be a major component of the surface. Fresh bright flows cover about two-percent of the surface, similar to the coverage by dark flows.</p><p>The images were taken at a distance of 15,000 kilometers (9,400 miles) from Io. North is 13 degrees to the left of up. 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/PIA02539" onclick="window.open(this.href); return false;" title="Voir l'image PIA02539: Bright Lava Flows at Emakong Patera, Io sur le site de la NASA">Voir l'image PIA02539: Bright Lava Flows at Emakong Patera, Io sur le site de la NASA.</a></div>
PIA02539: Bright Lava Flows at Emakong Patera, Io
<h1>PIA02540: Rifting at Hi'iaka Patera, Io?</h1><div class="PIA02540" lang="en" style="width:381px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>NASA's Galileo spacecraft acquired the images in this mosaic of Hi-iaka Patera (the irregularly shaped, dark depression at the center of the image) and two nearby mountains on November 25, 1999 during its 25th orbit. The sharp peak at the top of the image is about 11 kilometers (about 36,300 feet) high, and the two elongated plateaus to the west and south of the caldera are both about 3.5 kilometers (11,500 feet) high. The ridges on the northwestern mountain are often seen on Ionian mountains and are thought to be formed as surface material slides downslope due to gravity.</p><p>At low resolution, many of the dark features, called pateras, appear to be calderas -- depressions formed by collapse into an empty magma chamber. However, higher resolution images such as this one suggest a different origin. In the case of Hi-iaka, the northern and southern margins of the pateras have very similar shapes which appear to fit together. This may indicate that the crust has been pulled apart here and the resulting depression has subsequently been covered by dark lava flows. Furthermore, the two mountains bordering Hi-iaka Patera also appear to fit together. However, the similar shapes and heights of the pateras margins and mountains could be coincidental. Galileo scientists are currently investigating whether mountains and pateras are related to each other and what could cause the surface of Io to rift apart in such a manner.</p><p>North is to the top of the mosaic and the sun is illuminating the surface from the left. The resolution is 260 meters (about 280 yards) per picture element. Galileo took the images at a distance of 26,000 kilometers(16,000 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>.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02540" onclick="window.open(this.href); return false;" title="Voir l'image PIA02540: Rifting at Hi'iaka Patera, Io? sur le site de la NASA">Voir l'image PIA02540: Rifting at Hi'iaka Patera, Io? sur le site de la NASA.</a></div>
PIA02540: Rifting at Hi'iaka Patera, Io?
<h1>PIA02545: Eruption at Tvashtar Catena, Io, in color</h1><div class="PIA02545" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>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.</p><p>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 mesas 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.</p><p>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).</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/PIA02545" onclick="window.open(this.href); return false;" title="Voir l'image PIA02545: Eruption at Tvashtar Catena, Io, in color sur le site de la NASA">Voir l'image PIA02545: Eruption at Tvashtar Catena, Io, in color sur le site de la NASA.</a></div>
PIA02545: Eruption at Tvashtar Catena, Io, in color
<h1>PIA02546: Sulfur Gas in Pele's Plume</h1><div class="PIA02546" lang="en" style="width:710px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>This image depicts the discovery of sulfur gas in the plume of the Pele volcano on Jupiter's moon Io, as seen by the Hubble Space Telescope in October 1999, during a flyby of Io by NASA's Galileo spacecraft. The main image shows Io passing in front of Jupiter as seen by Hubble's Wide-Field Planetary Camera (WFPC2) in near-ultraviolet light. The small inset shows that when a WFPC2 image at shorter ultraviolet wavelengths is included in a color composite with the near-ultraviolet image, Io's Pele plume appears as a dark smudge off the edge of Io's disk, silhouetted against Jupiter. The larger inset shows data from Hubble's Space Telescope Imaging Spectrograph, which mapped the composition of Pele's plume by analyzing the ultraviolet light from Jupiter which had passed through the plume. The regions shown in yellow were rich in sulfur gas, which was precisely centered over the Pele volcano, whose position is shown along with the edge of Io's disk.</p><p>Additional information about the Hubble Space Telescope is available at<a href="http://www.stsci.edu/">http://www.stsci.edu/</a>. Additional information about the Galileo mission is available 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/PIA02546" onclick="window.open(this.href); return false;" title="Voir l'image PIA02546: Sulfur Gas in Pele's Plume sur le site de la NASA">Voir l'image PIA02546: Sulfur Gas in Pele's Plume sur le site de la NASA.</a></div>
PIA02546: Sulfur Gas in Pele's Plume