Galerie de photos de Japet, satellite de la planète Saturne

Iapetus_orbit.jpg
Iapetus_orbit.jpg
<h1>PIA00348: Iapetus Bright and Dark Terrains</h1><div class="PIA00348" lang="en" style="width:325px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">Saturn's outermost large moon, Iapetus, has a bright, heavily cratered icy terrain and a dark terrain, as shown in this Voyager 2 image taken on August 22, 1981. Amazingly, the dark material covers precisely the side of Iapetus that leads in the direction of orbital motion around Saturn (except for the poles), whereas the bright material occurs on the trailing hemisphere and at the poles. The bright terrain is made of dirty ice, and the dark terrain is surfaced by carbonaceous molecules, according to measurements made with Earth-based telescopes. Iapetus' dark hemisphere has been likened to tar or asphalt and is so dark that no details within this terrain were visible to Voyager 2. The bright icy hemisphere, likened to dirty snow, shows many large impact craters. The closest approach by Voyager 2 to Iapetus was a relatively distant 600,000 miles, so that our best images, such as this, have a resolution of about 12 miles. The dark material is made of organic substances, probably including poisonous cyano compounds such as frozen hydrogen cyanide polymers. Though we know a little about the dark terrain's chemical nature, we do not understand its origin. Two theories have been developed, but neither is fully satisfactory--(1) the dark material may be organic dust knocked off the small neighboring satellite Phoebe and "painted" onto the leading side of Iapetus as the dust spirals toward Saturn and Iapetus hurtles through the tenuous dust cloud, or (2) the dark material may be made of icy-cold carbonaceous "cryovolcanic" lavas that were erupted from Iapetus' interior and then blackened by solar radiation, charged particles, and cosmic rays. A determination of the actual cause, as well as discovery of any other geologic features smaller than 12 miles across, awaits the Cassini Saturn orbiter to arrive in 2004.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA00348" onclick="window.open(this.href); return false;" title="Voir l'image PIA00348: Iapetus Bright and Dark Terrains sur le site de la NASA">Voir l'image PIA00348: Iapetus Bright and Dark Terrains sur le site de la NASA.</a></div>
PIA00348: Iapetus Bright and Dark Terrains
<h1>PIA02268: Iapetus</h1><div class="PIA02268" lang="en" style="width:190px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">A large circular feature about 200 kilometers (120 miles) across with a dark spot in its center is visible in this photograph of Saturn's satellite Iapetus taken Nov. 12, 1980 from a distance of 3.2 million kilometers (1.9 million miles). The satellite's leading hemisphere is to the left, and the trailing hemisphere, which is about four to five times brighter, is to the right. The large circular feature is most probably a large impact structure outlined by dark material, possibly thrown out by the impact. The Voyager Project is managed for NASA by the Jet Propulsion Laboratory, Pasadena, Calif.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA02268" onclick="window.open(this.href); return false;" title="Voir l'image PIA02268: Iapetus sur le site de la NASA">Voir l'image PIA02268: Iapetus sur le site de la NASA.</a></div>
PIA02268: Iapetus
<h1>PIA05411: Saturn's Yin-Yang Moon</h1><div class="PIA05411" lang="en" style="width:640px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>This Cassini image hints at the split personality of Saturn's 1,436 kilometer (892 mile)-wide moon Iapetus. The Voyager spacecraft first imaged this curious yin-yang moon, with its light and dark hemispheres. The dark hemisphere is the side of Iapetus that leads in its orbit. In this view, both light and dark areas are visible.</p><p>The image was taken in visible light with the Cassini spacecraft's narrow angle camera on May 23, 2004, from a distance of 20.2 million kilometers (12.5 million miles) from Iapetus. The image scale is 121 kilometers (75 miles) per pixel. The image was magnified to aid visibility.</p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Office of Space Science, Washington, D.C. The Cassini orbiter and its two onboard cameras, were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.</p><p>For more information, about the Cassini-Huygens mission visit, <a href="http://saturn.jpl.nasa.gov/">http://saturn.jpl.nasa.gov</a> and the Cassini imaging team home page, <a href="http://ciclops.org/">http://ciclops.org</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA05411" onclick="window.open(this.href); return false;" title="Voir l'image PIA05411: Saturn's Yin-Yang Moon sur le site de la NASA">Voir l'image PIA05411: Saturn's Yin-Yang Moon sur le site de la NASA.</a></div>
PIA05411: Saturn's Yin-Yang Moon
<h1>PIA06100: Saturn's Two-Face Moon</h1><div class="PIA06100" lang="en" style="width:442px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>The moon with the split personality, Iapetus, presents a puzzling appearance. One hemisphere of the moon is very dark, while the other is very bright. Whether the moon is being coated by foreign material or being resurfaced by material from within is not yet known.</p><p>Iapetus' diameter is about one third that of our own moon at 1,436 kilometers (892 miles). The latest image was taken in visible light with the Cassini spacecraft narrow angle camera on July 3, 2004, from a distance of 3 million kilometers (1.8 million miles) from Iapetus (pronounced eye-APP-eh-tuss). </p><p>The brightness variations in this image are not due to shadowing, they are real. The face of Iapetus visible was observed at a Sun-Iapetus-spacecraft, or phase, angle of about 10 degrees. The image scale is 18 kilometers (11 miles) per pixel. The image was magnified by a factor of two to aid visibility.</p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Office of Space Science, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.</p><p>For more information, about the Cassini-Huygens mission visit, <a href="http://saturn.jpl.nasa.gov/">http://saturn.jpl.nasa.gov</a> and the Cassini imaging team home page, <a href="http://ciclops.org/">http://ciclops.org</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA06100" onclick="window.open(this.href); return false;" title="Voir l'image PIA06100: Saturn's Two-Face Moon sur le site de la NASA">Voir l'image PIA06100: Saturn's Two-Face Moon sur le site de la NASA.</a></div>
PIA06100: Saturn's Two-Face Moon
<h1>PIA06145: Waning Iapetus</h1><div class="PIA06145" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>These spectacular Cassini images of Saturn's moon Iapetus show an enticing world of contrasts.</p><p>These are the sharpest views of Iapetus from Cassini so far, and they represent better resolution than the best images of this moon achieved by NASA's Voyager spacecraft. Images obtained using ultraviolet (centered at 338 nanometers), green (568 nanometers) and infrared (930 nanometers) filters were combined to produce the enhanced color views at left and center; the image at the right was obtained in visible white light. The images on the bottom row are identical to those on top, with the addition of an overlying coordinate grid.</p><p>These views show parts of the moon's anti-Saturn side--the side that faces away from the ringed planet--which will not be imaged again by Cassini until Sept., 2007. In the central view, part of the moon's eastern edge was not imaged and appears to be cut off.</p><p>With a diameter of 1,436 kilometers (892 miles), Iapetus is Saturn's third largest moon. It is famous for the dramatic contrasts in brightness on its surface--the leading hemisphere is as dark as a freshly-tarred street, and the trailing hemisphere and poles almost as bright as snow.</p><p>Many impact craters can be seen in the bright terrain and in the transition zone between bright and dark, and for the first time in parts of the dark terrain. Also visible is a line of mountains that appear as a string of bright dots in the two color images at left, and on the eastern limb in the image at right. These mountains were originally detected in Voyager images, and might compete in height with the tallest mountains on Earth, Jupiter's moon Io and possibly even Mars. Further observations will be required to precisely determine their heights. Interestingly, the line of peaks is aligned remarkably close to the equator of Iapetus.</p><p>The large circular feature rotating into view in the southern hemisphere is probably an impact structure with a diameter of more than 400 kilometers (250 miles), and was first seen in low-resolution Cassini images just two months earlier.</p><p>Theses images were taken with the Cassini spacecraft narrow angle camera between Oct, 15 and 20, 2004, at distances of 1.2, 1.1 and 1.3 million kilometers (746,000, 684,000 and 808,000 miles) from Iapetus, respectively. The Sun-Iapetus-spacecraft, or phase, angle changes from 88 to 144 degrees across the three images. The image scale is approximately 7 kilometers (4.5 miles) per pixel.</p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Office of Space Science, Washington, D.C. The Cassini orbiter and its two onboard cameras, were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.</p><p>For more information, about the Cassini-Huygens mission visit, <a href="http://saturn.jpl.nasa.gov/">http://saturn.jpl.nasa.gov</a> and the Cassini imaging team home page, <a href="http://ciclops.org/">http://ciclops.org</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA06145" onclick="window.open(this.href); return false;" title="Voir l'image PIA06145: Waning Iapetus sur le site de la NASA">Voir l'image PIA06145: Waning Iapetus sur le site de la NASA.</a></div>
PIA06145: Waning Iapetus
<h1>PIA06146: Seeing in the Dark</h1><div class="PIA06146" lang="en" style="width:400px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>New details on Iapetus are illuminated by reflected light from Saturn in this revealing Cassini image. Never-before-seen features on the Saturn-facing part of Iapetus' bright trailing hemisphere are visible for the first time, including many dark spots, and a sharper view of a dark, circular structure that was first seen at very low resolution by NASA's Voyager 1 in 1980. Iapetus diameter is 1,436 kilometers (892 miles).</p><p>The image shows mainly the night side of Iapetus; part of the far brighter sunlit side appears at the right and is overexposed due to the long integration time of 180 seconds. Despite this long exposure time, almost no blurring due to the spacecraft's motion is apparent. This technique for imaging the night side of Iapetus will be used again during a flyby on Jan. 1, 2005, when Cassini will pass 13 times closer to the icy moon.</p><p>The image was taken in visible light with the Cassini spacecraft narrow angle camera on Oct. 22, 2004, at a distance of 1.6 million kilometers (994,000 miles) from Iapetus, and from a Sun-Iapetus-spacecraft, or phase, angle of 161 degrees. The view is centered on 0.4 degrees north latitude, 317 degrees west longitude on Iapetus. The image scale is 9.4 kilometers (5.8 miles) per pixel. </p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Office of Space Science, Washington, D.C. The Cassini orbiter and its two onboard cameras, were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.</p><p>For more information, about the Cassini-Huygens mission visit, <a href="http://saturn.jpl.nasa.gov/">http://saturn.jpl.nasa.gov</a> and the Cassini imaging team home page, <a href="http://ciclops.org/">http://ciclops.org</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA06146" onclick="window.open(this.href); return false;" title="Voir l'image PIA06146: Seeing in the Dark sur le site de la NASA">Voir l'image PIA06146: Seeing in the Dark sur le site de la NASA.</a></div>
PIA06146: Seeing in the Dark
<h1>PIA06165: Iapetus' New Year's Flyby</h1><div class="PIA06165" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p><a href="/figures/PIA06165_fig1.jpg"></a><br>Figure 1</p><p>This map of the surface of Saturn's moon Iapetus (1,436 kilometers, or 892 miles across), generated from images taken by NASA's Voyager spacecraft, illustrates the imaging coverage planned during Cassini's flyby on Dec. 31, 2004.</p><p>Cassini will glide past Iapetus at a distance of approximately 123,400 kilometers (76,700 miles) on New Year's Eve, at a speed of about 2 kilometers per second (4,474 miles per hour). Imaging coverage will be focused primarily on the dark terrain of Iapetus' leading hemisphere, in the area known as Cassini Regio. The spacecraft's namesake, Jean-Dominique Cassini, discovered Iapetus in 1672 and was only able to see the moon's bright trailing hemisphere.</p><p>In figure 1, colored lines on the map enclose regions that will be covered at different imaging scales as Cassini approaches Iapetus.</p><p>Images from Cassini's flyby will be superior in resolution to those obtained by Voyager 2 in August 1981. Voyager 2 passed Iapetus at a distance of approximately 909,000 kilometers (564,800 miles) at closest approach, yielding a best resolution image of about 8 kilometers per pixel. The resolution of Cassini images from this flyby will be 1.5 kilometers per pixel and better.</p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.</p><p>For more information about the Cassini-Huygens mission visit <a href="http://saturn.jpl.nasa.gov">http://saturn.jpl.nasa.gov</a>. For additional images visit the Cassini imaging team homepage <a href="http://ciclops.org">http://ciclops.org</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA06165" onclick="window.open(this.href); return false;" title="Voir l'image PIA06165: Iapetus' New Year's Flyby sur le site de la NASA">Voir l'image PIA06165: Iapetus' New Year's Flyby sur le site de la NASA.</a></div>
PIA06165: Iapetus' New Year's Flyby
<h1>PIA06166: Encountering Iapetus</h1><div class="PIA06166" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>On New Year's Eve 2004, Cassini flew past Saturn's intriguing moon Iapetus, capturing the four visible light images that were put together to form this global view.</p><p>The scene is dominated by a dark, heavily-cratered region, called Cassini Regio, that covers nearly an entire hemisphere of Iapetus. Iapetus is 1,436 kilometers (892 miles) across. The view is centered on the moon’s equator and on roughly 90 degrees west longitude -- a location that always faces the direction of Iapetus's orbital motion around Saturn.</p><p>Within Cassini Regio, and especially near the equator, dark deposits with a visual reflectivity of only about 4 percent coat nearly everything with remarkable uniformity. However, at latitudes of about 40 degrees, the surface transitions to a much brighter, icy terrain near the pole where the brightest icy materials have reflectivity over 60 percent. However, this region is not uniform: Close inspection reveals that the surface is stained by crudely north-south trending wispy streaks of darker material, typically a few kilometers wide and sometimes tens of kilometers long.</p><p>An ancient, 400-kilometer wide (250 miles) impact basin appears just above the center of the disc. The basin is heavily overprinted by more recent, smaller impact craters. The basin rim is delineated by steep scarps that descend to the basin floor. Many of these scarps, as well as walls of nearby craters, appear bright, probably due to exposed outcrops of relatively clean ice. Particularly at mid-latitudes, the brightest scarp exposures appear to face away from the equator (i.e. toward the pole). Often, the opposite south-facing scarps are stained with the lower-brightness material.</p><p>The most unique, and perhaps most remarkable feature discovered on Iapetus in Cassini images is a topographic ridge that coincides almost exactly with the geographic equator. The ridge is conspicuous in the picture as an approximately 20-kilometer wide (12 miles) band that extends from the western (left) side of the disc almost to the day/night boundary on the right. On the left horizon, the peak of the ridge reaches at least 13 kilometers (8 miles) above the surrounding terrain. Along the roughly 1,300 kilometer (800 mile) length over which it can be traced in this picture, it remains almost exactly parallel to the equator within a couple of degrees. The physical origin of the ridge has yet to be explained. It is not yet clear whether the ridge is a mountain belt that has folded upward, or an extensional crack in the surface through which material from inside Iapetus erupted onto the surface and accumulated locally, forming the ridge.</p><p>The origin of Cassini Regio is a long-standing debate among scientists. One theory proposes that its dark material may have erupted onto Iapetus's icy surface from the interior. Another theory holds that the dark material represented accumulated debris ejected by impact events on dark, outer satellites of Saturn. Details of this Cassini image mosaic do not definitively rule out either of the theories. However, they do provide important new insights and constraints.</p><p>The uniform appearance of the dark materials at the equator, the apparent thinning and spottiness of the dark materials at progressively higher latitudes and dark wispy streaks near the distal margin of Cassini Regio strongly suggest that dark material was emplaced as a coating. One of the important new results is that no clear evidence can be found that erupted fluids have resurfaced Cassini Regio. The high density of impact craters argues that the terrain underlying the dark coating is relatively ancient and has not been eradicated by its emplacement. Thus, Cassini Regio may have had its origin in plume-style eruptions in which dark particulate materials accumulated on the surface as fallout, perhaps in conjunction with the creation of the equatorial ridge. On the other hand, the dark deposits in Cassini Regio may be a surface coating consistent with, and perhaps more simply explained by, the fall of dark materials from outside.</p><p>The view has been oriented so that the north pole is toward the top of the picture.</p><p>Cassini acquired the images in this mosaic with its narrow angle camera on Dec. 31, 2004, at a distance of about 172,400 kilometers (107,124 miles) from Iapetus and at a Sun-Iapetus-spacecraft, or phase, angle of 50 degrees. The image scale is 1 kilometer (0.6 miles) per pixel. The image has been contrast enhanced to aid visibility of surface features. </p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.</p><p>For more information about the Cassini-Huygens mission visit <a href="http://saturn.jpl.nasa.gov">http://saturn.jpl.nasa.gov</a>. For images visit the Cassini imaging team home page <a href="http://ciclops.org">http://ciclops.org</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA06166" onclick="window.open(this.href); return false;" title="Voir l'image PIA06166: Encountering Iapetus sur le site de la NASA">Voir l'image PIA06166: Encountering Iapetus sur le site de la NASA.</a></div>
PIA06166: Encountering Iapetus
<h1>PIA06167: Dark-stained Iapetus</h1><div class="PIA06167" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>This near-true color view from Cassini reveals the colorful and intriguing surface of Saturn's moon Iapetus in unrivaled clarity.</p><p>The images taken with different spectral filters and used for this composite were taken at the same time as the clear frames used in <a href="/catalog/PIA06166">PIA06166</a>. The use of color on Iapetus is particularly helpful for discriminating between shadows (which appear black) and the intrinsically dark terrain (which appears brownish).</p><p>This image shows the northern part of the dark Cassini Regio and the transition zone to a brighter surface at high northern latitudes. Within the transition zone, the surface is stained by roughly north-south trending wispy streaks of dark material. The absence of an atmosphere on Iapetus means that the material was deposited by some means other than precipitation, such as ballistic placement from impacts occurring elsewhere on Iapetus, or was captured from elsewhere in the Saturn system.</p><p>Iapetus’s north pole is not visible here, nor is any part of the bright trailing hemisphere.</p><p>Images taken with infrared (centered at 930 nanometers), green (568 nanometers), and ultraviolet light (338 nanometers) filters were combined to create this image. The view was obtained with the Cassini spacecraft narrow angle camera on Dec. 31, 2004, at a distance of about 172,900 kilometers (107,435 miles) from Iapetus. Resolution achieved in the original image was 1 kilometer (0.6 miles) per pixel. The image has been magnified by a factor of two to aid visibility of surface features. </p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.</p><p>For more information about the Cassini-Huygens mission visit <a href="http://saturn.jpl.nasa.gov">http://saturn.jpl.nasa.gov</a>. For images visit the Cassini imaging team home page <a href="http://ciclops.org">http://ciclops.org</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA06167" onclick="window.open(this.href); return false;" title="Voir l'image PIA06167: Dark-stained Iapetus sur le site de la NASA">Voir l'image PIA06167: Dark-stained Iapetus sur le site de la NASA.</a></div>
PIA06167: Dark-stained Iapetus
<h1>PIA06168: Iapetus by Saturn Shine</h1><div class="PIA06168" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>This almost surreal view of Iapetus was acquired by Cassini about 10 minutes after the spacecraft's closest approach to the icy moon during a close flyby on New Year's Eve 2004.</p><p>The image shows Iapetus' surface illuminated by reflected light from Saturn (not by the Sun) and is the highest resolution view acquired to date of this part of Iapetus' surface. </p><p>Compared to the approximately one second exposure times used for imaging Iapetus' sunlit side, this view required a very long exposure time of 82 seconds. Cassini was designed to pivot while moving in order to keep its cameras and other remote sensing instruments pointed 'on target' with great precision. Consequently, despite the large relative speed between Iapetus and the spacecraft during this long exposure -- about 2 kilometers per second or almost 4,500 miles per hour at closest approach -- the image of the moon’s surface is un-smeared (although the background stars are smeared).</p><p>This image reveals a heavily cratered surface and shows the boundary between Iapetus' bright trailing hemisphere and Cassini Regio -- a large, dark region that covers the leading hemisphere of the moon’s surface. Some of the dark material appears to have collected inside the rim of a large impact structure about 250 kilometers across (155 miles) that lies just beyond the edge of the dark region (seen here near the right of the image). NASA's Voyager images (see <a href="/catalog/PIA02268">PIA02268</a>) this feature appeared as a dark 'moat' and had been hypothesized to be an impact structure. The recent images from Cassini confirm an impact origin for this feature.</p><p>In contrast, the origin of the dark material is currently unknown and the recent images have sparked exciting debates among Cassini imaging scientists. Some characteristics of the dark region revealed in this and other images taken during the encounter suggest that dark material from elsewhere in the Saturnian system -- perhaps the result of an impact on another nearby moon -- has coated this side of Iapetus with a relatively thin layer. However, an internal origin for the material has not been ruled out and, if correct, may be related to the long equatorial ridge discovered in Cassini images to span Cassini Regio. </p><p>Regardless of its origins, the dark material appears to lie on top of other geologic features seen on Iapetus thus far, implying that the event which formed the dark coating occurred later in Iapetus' history. A closer encounter with this moon later in the Cassini mission (September 2007) may reveal more detail and help answer the question of the origin and age of the dark material on Iapetus.</p><p>The image was obtained in visible light with the Cassini spacecraft narrow angle camera on Dec. 31, 2004, at a distance of about 123,370 kilometers (76,659 miles) from Iapetus. The image scale is 730 meters (2,395 feet) per pixel. The image has been contrast enhanced to aid visibility of surface features. </p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.</p><p>For more information about the Cassini-Huygens mission visit <a href="http://saturn.jpl.nasa.gov">http://saturn.jpl.nasa.gov</a>. For images visit the Cassini imaging team home page <a href="http://ciclops.org">http://ciclops.org</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA06168" onclick="window.open(this.href); return false;" title="Voir l'image PIA06168: Iapetus by Saturn Shine sur le site de la NASA">Voir l'image PIA06168: Iapetus by Saturn Shine sur le site de la NASA.</a></div>
PIA06168: Iapetus by Saturn Shine
<h1>PIA06169: Iapetus in 3D</h1><div class="PIA06169" lang="en" style="width:749px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>This stereo view of Iapetus was created by combining two Cassini images, which were taken one day apart. The view serves mainly to show the spherical shape of Iapetus and some of the moon’s topography.</p><p>The prominent linear ridge in the center of the dark area -- a place known as Cassini Regio -- marks the equator quite closely. The ridge was first discovered in this set of images and was seen at higher resolution in images taken during Cassini’s flyby of Iapetus on New Year’s Eve 2004. Some Cassini imaging scientists have suggested that the ridge may have a causal relationship to the dark material that coats the moon’s leading hemisphere. The mountain on the left is part of the ridge, and rises at least 13 kilometers (8 miles) above the surrounding terrain. </p><p>The large basin near the terminator (at upper right) was detected in Cassini images from July and has a diameter of about 550 kilometers (340 miles). The large basin at upper left was newly detected in these images. The crater at far right (within the bright terrain) was known from the days of NASA's Voyager missions.</p><p>North on Iapetus is towards the upper left. The images were obtained in visible light with the Cassini spacecraft narrow angle camera on Dec. 26 and 27, 2004. Cassini’s distance from Iapetus ranged from 880,537 to 716,678 kilometers (547,140 to 445,323 miles) between the two images, and the Sun-Iapetus-spacecraft, or phase, angle changed from 21 to 22 degrees. Resolution achieved in the original images was 5.2 and 4.3 kilometers (3.2 and 2.7 miles) per pixel, respectively. </p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.</p><p>For more information about the Cassini-Huygens mission visit <a href="http://saturn.jpl.nasa.gov">http://saturn.jpl.nasa.gov</a>. For images visit the Cassini imaging team home page <a href="http://ciclops.org">http://ciclops.org</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA06169" onclick="window.open(this.href); return false;" title="Voir l'image PIA06169: Iapetus in 3D sur le site de la NASA">Voir l'image PIA06169: Iapetus in 3D sur le site de la NASA.</a></div>
PIA06169: Iapetus in 3D
<h1>PIA06170: Iapetus: A View from the Top</h1><div class="PIA06170" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>This oblique view of Saturn's moon Iapetus from high latitude shows how the dark, heavily cratered terrain of Cassini Regio transitions to a bright, icy terrain at high latitudes.</p><p>In this mosaic of two high resolution images taken during Cassini’s New Year’s Eve 2004 flyby of Iapetus, the direction toward the north pole is approximately 15 degrees below the horizontal on the right. At the equator terrains are uniformly covered with a dark mantle of material that has a reflectivity of about 4 percent. At latitudes toward the pole of about 40 degrees, the dark deposits become patchy and diffuse as the surface transitions to a much brighter, icy terrain near the pole. The brightest icy materials exhibit visual reflectivity over 60 percent.</p><p>Superimposed on the bright terrain is a subtle, ghostly pattern of crudely parallel, north-south trending wispy streaks. The streaks, which were discovered during this flyby of Iapetus, are typically a few kilometers wide and sometimes tens of kilometers long. Their appearance and orientation may be connected with the emplacement of dark materials that cover Cassini Regio. The dark materials might represent the gradual accumulation of dark debris falling from space, or alternatively, may represent fallout from plume-style eruptions that may have accompanied the formation of Iapetus's enigmatic equatorial ridge (see <a href="/catalog/PIA06166">PIA06166</a>).</p><p>Also seen in this mosaic are conspicuous, north-facing bright crater walls. An example can be seen in the upper left where the bright, 4-kilometer-high (2.5 miles) walls of a 70 kilometer (44 mile) central-peak crater lies. </p><p>The bright crater walls are often higher in brightness than the corresponding south-facing walls of the same crater. They are vaguely reminiscent of bright north-facing crater walls that were discovered by NASA's Voyager and Galileo spacecraft in craters near the poles of the Jovian satellites Callisto and Ganymede. In the case of the Jovian satellites, cold-trapping of frosts on north-facing slopes and sublimation of ices from south-facing slopes are thought to produce the north-south asymmetries in crater wall brightness. However, the occurrence of some young-appearing craters on Iapetus that have bright north-facing and dark south-facing slopes, and the pattern of streaks near the north pole of Iapetus suggests that another mechanism may be responsible for the crater wall brightness asymmetries on Iapetus.</p><p>One possibility is that the south-facing slopes may be stained by the same process that emplaced the low brightness coating throughout the region. In this case, the north-pointing scarps might be bright because they face away and are shielded from the putative falling spray of dark materials. Bright south-facing slopes would exist primarily on young craters that have not been exposed to the darkening agent long enough to be stained.</p><p>The image was obtained in visible light with the Cassini spacecraft narrow angle camera on Dec. 31, 2004, at a distance of about 123,370 kilometers (76,658 miles) from Iapetus and at a Sun-Iapetus-spacecraft, or phase, angle of 93 degrees. Resolution achieved in the original image was 732 meters (2,401 feet) per pixel.</p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.</p><p>For more information about the Cassini-Huygens mission visit <a href="http://saturn.jpl.nasa.gov">http://saturn.jpl.nasa.gov</a>. For images visit the Cassini imaging team home page <a href="http://ciclops.org">http://ciclops.org</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA06170" onclick="window.open(this.href); return false;" title="Voir l'image PIA06170: Iapetus: A View from the Top sur le site de la NASA">Voir l'image PIA06170: Iapetus: A View from the Top sur le site de la NASA.</a></div>
PIA06170: Iapetus: A View from the Top
<h1>PIA06171: Giant Landslide on Iapetus</h1><div class="PIA06171" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>A spectacular landslide within the low-brightness region of Iapetus's surface known as Cassini Regio is visible in this image from Cassini. Iapetus is one of the moons of Saturn.</p><p>The landslide material appears to have collapsed from a scarp 15 kilometers high (9 miles) that forms the rim of an ancient 600 kilometer (375 mile) impact basin. Unconsolidated rubble from the landslide extends halfway across a conspicuous, 120-kilometer diameter (75-mile) flat-floored impact crater that lies just inside the basin scarp.</p><p>Landslides are common geological phenomena on many planetary bodies, including Earth and Mars. The appearance of this landslide on an icy satellite with low-brightness cratered terrain is reminiscent of landslide features that were observed during NASA's Galileo mission on the Jovian satellite Callisto. The fact that the Iapetus landslide traveled many kilometers from the basin scarp could indicate that the surface material is very fine-grained, and perhaps was fluffed by mechanical forces that allowed the landslide debris to flow extended distances.</p><p>In this view, north is to the left of the picture and solar illumination is from the bottom of the frame. The image was obtained in visible light with the Cassini spacecraft narrow angle camera on Dec. 31, 2004, at a distance of about 123,400 kilometers (76,677 miles) from Iapetus and at a Sun-Iapetus-spacecraft, or phase, angle of 78 degrees. Resolution achieved in the original image was 740 meters (2,428 feet) per pixel. The image has been contrast-enhanced and magnified by a factor of two to aid visibility.</p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.</p><p>For more information about the Cassini-Huygens mission visit <a href="http://saturn.jpl.nasa.gov">http://saturn.jpl.nasa.gov</a>. For images visit the Cassini imaging team home page <a href="http://ciclops.org">http://ciclops.org</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA06171" onclick="window.open(this.href); return false;" title="Voir l'image PIA06171: Giant Landslide on Iapetus sur le site de la NASA">Voir l'image PIA06171: Giant Landslide on Iapetus sur le site de la NASA.</a></div>
PIA06171: Giant Landslide on Iapetus
<h1>PIA06466: Iapetus: Light and Dark</h1><div class="PIA06466" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>The dark material that coats one hemisphere of Saturn's moon Iapetus is very dark, as these two processed views of the same image demonstrate.</p><p>The image on the left has been cleaned of cosmic rays and magnified; in this otherwise un-enhanced view, only a small part of the moon's surface, at the bottom, is visible because it is part of the bright side of Iapetus. (Only the right hand side of Iapetus is illuminated by sunlight.) The same image, shown on the right, has been contrast-enhanced to make visible the part of the illuminated side of Iapetus that is coated with dark material. </p><p>The image was taken in visible light, with the Cassini spacecraft narrow angle camera on July 19, 2004, from a distance of 2.9 million kilometers (1.8 million miles) from Iapetus, and at a Sun-Iapetus-spacecraft, or phase angle of 89 degrees. The image scale is 17 kilometers (11 miles) per pixel. The image has been magnified by a factor of four to aid visibility. </p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Office of Space Science, Washington, D.C. The Cassini orbiter and its two onboard cameras, were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.</p><p>For more information, about the Cassini-Huygens mission visit, <a href="http://saturn.jpl.nasa.gov/">http://saturn.jpl.nasa.gov</a> and the Cassini imaging team home page, <a href="http://ciclops.org/">http://ciclops.org</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA06466" onclick="window.open(this.href); return false;" title="Voir l'image PIA06466: Iapetus: Light and Dark sur le site de la NASA">Voir l'image PIA06466: Iapetus: Light and Dark sur le site de la NASA.</a></div>
PIA06466: Iapetus: Light and Dark
<h1>PIA06521: Iapetus' Dark Side</h1><div class="PIA06521" lang="en" style="width:697px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>This image shows the dark, leading hemisphere of the mysterious moon Iapetus. The dark area is the Cassini region, named for Giovanni Cassini, who discovered the moon in 1672. The diameter of Iapetus is 1,436 kilometers (892 miles).</p><p>Cassini noted that he was able to see the moon on one side of its orbit around Saturn, but not on the other side. From this, he correctly deduced that one hemisphere must be dark while the other is much brighter.</p><p>The image was taken in visible light with the Cassini spacecraft narrow angle camera on Sept. 24, 2004, at a distance of 7.4 million kilometers (4.6 million miles) from Iapetus and at a Sun-Iapetus-spacecraft, or phase, angle of 51 degrees. The image scale is 45 kilometers (28 miles) per pixel. The image has been magnified by a factor of four to aid visibility.</p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.<p>For more information, about the Cassini-Huygens mission visit, <a href="http://saturn.jpl.nasa.gov/">http://saturn.jpl.nasa.gov</a> and the Cassini imaging team home page, <a href="http://ciclops.org/">http://ciclops.org</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA06521" onclick="window.open(this.href); return false;" title="Voir l'image PIA06521: Iapetus' Dark Side sur le site de la NASA">Voir l'image PIA06521: Iapetus' Dark Side sur le site de la NASA.</a></div>
PIA06521: Iapetus' Dark Side
<h1>PIA06646: Details in the Dark</h1><div class="PIA06646" lang="en" style="width:471px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>This view shows one of the huge impact basins on the terminator of Saturn's moon Iapetus and a smaller, but still fairly large, crater near the southern bright-dark boundary. Just visible near the western limb, in the dark territory of Cassini Regio, is the moon's mysterious equatorial ridge. The ridge was discovered in Cassini images (see <a href="/catalog/PIA06166">PIA06166</a>) and reaches 20 kilometers (12 miles) high in places.</p><p>This view shows principally the leading hemisphere on Iapetus. North is up and tilted 15 degrees to the right. Iapetus is 1,468 kilometers (912 miles) across.</p><p>The image was taken with the Cassini spacecraft narrow-angle camera on March 19, 2005, through spectral filters sensitive to wavelengths of infrared light centered at 752 nanometers. The view was acquired at a distance of approximately 1.4 million kilometers (880,000 miles) from Iapetus and at a Sun-Iapetus-spacecraft, or phase, angle of 70 degrees. Resolution in the original image was 8 kilometers (5 miles) per pixel.</p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.</p><p>For more information about the Cassini-Huygens mission, visit <a href="http://saturn.jpl.nasa.gov">http://saturn.jpl.nasa.gov</a> and the Cassini imaging team home page, <a href="http://ciclops.org">http://ciclops.org</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA06646" onclick="window.open(this.href); return false;" title="Voir l'image PIA06646: Details in the Dark sur le site de la NASA">Voir l'image PIA06646: Details in the Dark sur le site de la NASA.</a></div>
PIA06646: Details in the Dark
<h1>PIA07000: VIMS Iapetus Two Shooter</h1><div class="PIA07000" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>These two color composite images of Saturn's moon Iapetus from Cassini's visual and infrared mapping spectrometer were obtained on Dec. 31, 2004, an hour and a half before the New Year, at a distance of 121,000 kilometers (75,186 miles), with a spatial resolution of about 60 kilometers (37 miles). </p><p>The three colors used in the left mosaic correspond to 1.01, 1.51, and 2 microns, while the right mosaic is comprised of images at 3.0, 3.21, and 4.60 microns. The two images show the vast difference in the composition of the bright and dark regions of Iapetus. As one moves from the near infrared 1 to 2 micron spectral region (left image) to the 3 to 5 micron spectral region (right image) the bright, ice-rich region on Iapetus turns dark and the dark region rich in organics turns bright.</p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The visible and infrared mapping spectrometer team is based at the University of Arizona, Tucson.</p><p>For more information about the Cassini-Huygens mission visit, <a href="http://saturn.jpl.nasa.gov">http://saturn.jpl.nasa.gov</a>. For more information about the visual and infrared mapping spectrometer visit <a href="http://wwwvims.lpl.arizona.edu/">http://wwwvims.lpl.arizona.edu/</a>. </p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA07000" onclick="window.open(this.href); return false;" title="Voir l'image PIA07000: VIMS Iapetus Two Shooter sur le site de la NASA">Voir l'image PIA07000: VIMS Iapetus Two Shooter sur le site de la NASA.</a></div>
PIA07000: VIMS Iapetus Two Shooter
<h1>PIA07660: A Moon with Two Dark Sides</h1><div class="PIA07660" lang="en" style="width:743px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>Although it is no longer uncharted land, the origin of the dark territory of Cassini Regio on Iapetus remains a mystery. Also puzzling is the equatorial ridge that bisects this terrain, and how it fits into the story of the moon's strange brightness dichotomy. The ridge is seen here, curving along the lower left edge of Iapetus.</p><p>The view looks down onto the northern hemisphere of Iapetus (1,468 kilometers, or 912 miles across), and shows terrain on the moon's leading hemisphere.</p><p>The image was taken in polarized green light with the Cassini spacecraft narrow-angle camera on Nov. 12, 2005 at a distance of approximately 417,000 kilometers (259,000 miles) from Iapetus and at a Sun-Iapetus-spacecraft, or phase, angle of 95 degrees. Image scale is about 2 kilometers (1 mile) per pixel.</p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.</p><p>For more information about the Cassini-Huygens mission visit <a href="http://saturn.jpl.nasa.gov">http://saturn.jpl.nasa.gov</a>. The Cassini imaging team homepage is at <a href="http://ciclops.org">http://ciclops.org</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA07660" onclick="window.open(this.href); return false;" title="Voir l'image PIA07660: A Moon with Two Dark Sides sur le site de la NASA">Voir l'image PIA07660: A Moon with Two Dark Sides sur le site de la NASA.</a></div>
PIA07660: A Moon with Two Dark Sides
<h1>PIA07766: Iapetus Spins and Tilts</h1><div class="PIA07766" lang="en" style="width:618px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p><a href="/archive/PIA07766.mov"></a><b><br />Click on image for Iapetus Spins and Tilts Movie</b></p><p>Saturn's two-faced moon tilts and rotates for Cassini in this mesmerizing movie sequence of images acquired during the spacecraft's close encounter with Iapetus on Nov. 12, 2005.</p><p>The encounter begins with Cassini about 850,000 kilometers (530,000 miles) from Iapetus. Cassini approached over the moon's northern hemisphere, allowing for excellent full views of a 575-kilometer-wide (360-mile) impact basin in northeastern Cassini Regio. Astronomer Giovanni Cassini discovered the light and dark faces of Iapetus' two hemispheres (among his other Saturn discoveries), and the dark region. The spacecraft also bears his name.</p><p>Also prominent in these images is a 380-kilometer-wide (235-mile) basin to the northwest of the larger basin, in the transition zone between Cassini Regio and a brighter region called Roncevaux Terra, with its 150-kilometer-wide (95-mile) crater Roland (at the top, with a prominent central peak).</p><p>The movie takes Cassini to its closest approach, at about 415,000 kilometers (260,000 miles) from Iapetus, and then looks back at the moon's receding crescent. The sequence ends with Cassini at a distance of about 460,000 kilometers (285,000 miles) from the moon.</p><p>Iapetus is 1,468 kilometers (912 miles) across.</p><p>Images taken using ultraviolet, green and infrared spectral filters with the Cassini spacecraft narrow-angle camera were combined to create false-color frames for this movie. The color seen here is similar to that produced in (red, green and blue) natural color views. Resolution in the original images taken at closest approach to Iapetus was about 3 kilometers (2 miles) per pixel. The color frames were resized to create the movie. </p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.</p></p>For more information about the Cassini-Huygens mission visit <a href="http://saturn.jpl.nasa.gov">http://saturn.jpl.nasa.gov</a>. The Cassini imaging team homepage is at <a href="http://ciclops.org">http://ciclops.org</a>.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA07766" onclick="window.open(this.href); return false;" title="Voir l'image PIA07766: Iapetus Spins and Tilts sur le site de la NASA">Voir l'image PIA07766: Iapetus Spins and Tilts sur le site de la NASA.</a></div>
PIA07766: Iapetus Spins and Tilts
<h1>PIA08125: To the Relief of Iapetus</h1><div class="PIA08125" lang="en" style="width:638px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>Sunlight strikes the terminator (the boundary between day and night) region on Saturn's moon Iapetus at nearly horizontal angles, making visible the vertical relief of many features.</p><p>This view is centered on terrain in the southern hemisphere of Iapetus (1,468 kilometers, or 912 miles across). Lit terrain visible here is on the moon's leading hemisphere. In this image, a large, central-peaked crater is notable at the boundary between the dark material in Cassini Regio and the brighter material on the trailing hemisphere.</p><p>The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Jan. 22, 2006, at a distance of approximately 1.3 million kilometers (800,000 miles) from Iapetus and at a Sun-Iapetus-spacecraft, or phase, angle of 67 degrees. Resolution in the original image was 8 kilometers (5 miles) per pixel. The image has been magnified by a factor of two and contrast-enhanced to aid visibility.</p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.</p><p>For more information about the Cassini-Huygens mission visit <a href="http://saturn.jpl.nasa.gov">http://saturn.jpl.nasa.gov/home/index.cfm</a>. The Cassini imaging team homepage is at <a href="http://ciclops.org">http://ciclops.org</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA08125" onclick="window.open(this.href); return false;" title="Voir l'image PIA08125: To the Relief of Iapetus sur le site de la NASA">Voir l'image PIA08125: To the Relief of Iapetus sur le site de la NASA.</a></div>
PIA08125: To the Relief of Iapetus
<h1>PIA08164: From Dark to Bright and Red to White</h1><div class="PIA08164" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>Cassini's landmark investigation of Saturn's yin-yang moon Iapetus, with its bright and dark hemispheres, continues to provide insights into the nature of this intriguing body.</p><p>These two views of Iapetus primarily show terrain in the southern part of the moon's dark leading hemisphere -- the side of Iapetus that is coated with dark material. The bright south pole of Iapetus is visible, along with some terrain (at the bottom) that lies on the bright trailing hemisphere.</p><p>The dark terrain known as Cassini Regio is uniformly dark between the equator and about 30 degrees south latitude. From there down to about 50 to 60 degrees south latitude, the dark material looks "patchy" because south-facing crater walls are bright (being largely devoid of the dark material). South of this region, only some northward-facing crater walls are still dark, while the bright terrain has a somewhat reddish color.</p><p>See <a href="/catalog/PIA06167">PIA06167</a> for an up-close view of this transition in the northern hemisphere.</p><p>Beyond 90 degrees south (i.e., on the trailing side), the reddish color becomes white. The region at the bottom of the color view presented here shows this "color boundary" in the bright terrain, which also marks the boundary between the leading and trailing hemispheres.</p><p>Iapetus is 1,468 kilometers (912 miles) across. North is up in the monochrome image and rotated 16 degrees to the left in the color image.</p><p>The monochrome image on the left was taken using a filter sensitive to wavelengths of infrared light centered at 930 nanometers. The image was obtained with the Cassini spacecraft narrow-angle camera on April 8, 2006, at a distance of approximately 866,000 kilometers (538,000 miles) from Iapetus and at a Sun-Iapetus-spacecraft, or phase, angle of 88 degrees. The image scale is 5 kilometers (3 miles) per pixel.</p><p>The color view on the right was created by combining images taken in ultraviolet, green and infrared spectral filters. The images were acquired with the Cassini spacecraft narrow-angle camera on April 9, 2006, at a distance of approximately 692,000 kilometers (430,000 miles) from Iapetus and at a Sun-Iapetus-spacecraft, or phase, angle of 101 degrees. The image scale is 4 kilometers (2.5 miles) per pixel.</p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.</p><p>For more information about the Cassini-Huygens mission visit <a href="http://saturn.jpl.nasa.gov">http://saturn.jpl.nasa.gov/home/index.cfm</a>. The Cassini imaging team homepage is at <a href="http://ciclops.org">http://ciclops.org</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA08164" onclick="window.open(this.href); return false;" title="Voir l'image PIA08164: From Dark to Bright and Red to White sur le site de la NASA">Voir l'image PIA08164: From Dark to Bright and Red to White sur le site de la NASA.</a></div>
PIA08164: From Dark to Bright and Red to White
<h1>PIA08177: Mysterious Iapetus</h1><div class="PIA08177" lang="en" style="width:288px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>A distant glimpse of Iapetus reveals details within the dark terrain of Cassini Regio, including an impact basin at top that is roughly 400 kilometers (250 miles) wide.</p><p>Researchers remain unsure about the mechanism that has darkened the leading hemisphere. </p><p>This view looks toward the southern hemisphere on the leading side of Iapetus (1,468 kilometers, or 912 miles across). North is up.</p><p>The image was taken in visible light with the Cassini spacecraft narrow-angle camera on April 4, 2006, at a distance of approximately 1.4 million kilometers (900,000 miles) from Iapetus. The image scale is 9 kilometers (6 miles) per pixel.</p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.</p><p>For more information about the Cassini-Huygens mission visit <a href="http://saturn.jpl.nasa.gov">http://saturn.jpl.nasa.gov/home/index.cfm</a>. The Cassini imaging team homepage is at <a href="http://ciclops.org">http://ciclops.org</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA08177" onclick="window.open(this.href); return false;" title="Voir l'image PIA08177: Mysterious Iapetus sur le site de la NASA">Voir l'image PIA08177: Mysterious Iapetus sur le site de la NASA.</a></div>
PIA08177: Mysterious Iapetus
<h1>PIA08234: World of Contrast</h1><div class="PIA08234" lang="en" style="width:320px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>This Cassini spacecraft view shows how the bright and dark regions on Iapetus fit together like the seams of a baseball. Some of the material that covers the moon's dark, leading side spills over into regions on the brighter trailing side, creating the feature near upper right referred to by some scientists as "the Moat."</p><p>(See <a href="/catalog/PIA06168">PIA06168</a> for a higher resolution view of this region.)</p><p>The large impact basin above center in the dark terrain has a diameter of about 550 kilometers (340 miles).</p><p>This view looks toward the Saturn-facing hemisphere of Iapetus (1,468 kilometers, or 912 miles across). North is up.</p><p>The image was taken in visible light with the Cassini spacecraft narrow-angle camera on June 25, 2006 at a distance of approximately 1.6 million kilometers (1 million miles) from Iapetus. Image scale is 9 kilometers (6 miles) per pixel.</p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.</p><p>For more information about the Cassini-Huygens mission visit <a href="http://saturn.jpl.nasa.gov">http://saturn.jpl.nasa.gov/home/index.cfm</a>. The Cassini imaging team homepage is at <a href="http://ciclops.org">http://ciclops.org</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA08234" onclick="window.open(this.href); return false;" title="Voir l'image PIA08234: World of Contrast sur le site de la NASA">Voir l'image PIA08234: World of Contrast sur le site de la NASA.</a></div>
PIA08234: World of Contrast
<h1>PIA08273: Duotone Moon</h1><div class="PIA08273" lang="en" style="width:207px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>The many impact scars borne by Iapetus are made far more conspicuous in the region of transition from its dark hemisphere to its bright one. In this terrain, the dark material that coats Cassini Regio accentuates slopes and crater floors, creating a land of stark contrasts.</p><p>North on Iapetus (1,468 kilometers, or 912 miles across) is up.</p><p>The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Sept. 6, 2006 at a distance of approximately 2.2 million kilometers (1.4 million miles) from Iapetus and at a Sun-Iapetus-spacecraft, or phase, angle of 26 degrees. Image scale is 13 kilometers (8 miles) per pixel.</p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.</p><p>For more information about the Cassini-Huygens mission visit <a href="http://saturn.jpl.nasa.gov">http://saturn.jpl.nasa.gov/home/index.cfm</a>. The Cassini imaging team homepage is at <a href="http://ciclops.org">http://ciclops.org</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA08273" onclick="window.open(this.href); return false;" title="Voir l'image PIA08273: Duotone Moon sur le site de la NASA">Voir l'image PIA08273: Duotone Moon sur le site de la NASA.</a></div>
PIA08273: Duotone Moon
<h1>PIA08372: The Himalayas of Iapetus</h1><div class="PIA08372" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>This stunning close-up view shows mountainous terrain that reaches about 10 kilometers (6 miles) high along the unique equatorial ridge of Iapetus. The view was acquired during Cassini's only close flyby of the two-toned Saturn moon.</p><p>Above the middle of the image can be seen a place where an impact has exposed the bright ice beneath the dark overlying material.</p><p>The image was taken on Sept. 10, 2007, with the Cassini spacecraft narrow-angle camera at a distance of approximately 3,870 kilometers (2,400 miles) from Iapetus. Image scale is 23 meters (75 feet) per pixel.</p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.</p><p>For more information about the Cassini-Huygens mission visit <a href="http://saturn.jpl.nasa.gov">http://saturn.jpl.nasa.gov/home/index.cfm</a>. The Cassini imaging team homepage is at <a href="http://ciclops.org">http://ciclops.org</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA08372" onclick="window.open(this.href); return false;" title="Voir l'image PIA08372: The Himalayas of Iapetus sur le site de la NASA">Voir l'image PIA08372: The Himalayas of Iapetus sur le site de la NASA.</a></div>
PIA08372: The Himalayas of Iapetus
<h1>PIA08373: Coated Craters</h1><div class="PIA08373" lang="en" style="width:509px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>Cassini surveys a bright landscape coated by dark material on Iapetus. This image shows terrain in the transition region between the moon's dark leading hemisphere and its bright trailing hemisphere. The view was acquired during Cassini's only close flyby of the two-toned Saturn moon.</p><p>The image was taken on Sept. 10, 2007, with the Cassini spacecraft narrow-angle camera at a distance of approximately 5,260 kilometers (3,270 miles) from Iapetus. Image scale is 32 meters (105 feet) per pixel.</p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.</p><p>For more information about the Cassini-Huygens mission visit <a href="http://saturn.jpl.nasa.gov">http://saturn.jpl.nasa.gov/home/index.cfm</a>. The Cassini imaging team homepage is at <a href="http://ciclops.org">http://ciclops.org</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA08373" onclick="window.open(this.href); return false;" title="Voir l'image PIA08373: Coated Craters sur le site de la NASA">Voir l'image PIA08373: Coated Craters sur le site de la NASA.</a></div>
PIA08373: Coated Craters
<h1>PIA08374: Inky Stains on a Frozen Moon</h1><div class="PIA08374" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>Dark material splatters the walls and floors of craters in the surreal, frozen wastelands of Iapetus. This image shows terrain in the transition region between the moon's dark leading hemisphere and its bright trailing hemisphere. The view was acquired during Cassini's only close flyby of the two-toned Saturn moon.</p><p>The image was taken on Sept. 10, 2007, with the Cassini spacecraft narrow-angle camera at a distance of approximately 6,030 kilometers (3,750 miles) from Iapetus. Image scale is 36 meters (118 feet) per pixel.</p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.</p><p>For more information about the Cassini-Huygens mission visit <a href="http://saturn.jpl.nasa.gov">http://saturn.jpl.nasa.gov/home/index.cfm</a>. The Cassini imaging team homepage is at <a href="http://ciclops.org">http://ciclops.org</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA08374" onclick="window.open(this.href); return false;" title="Voir l'image PIA08374: Inky Stains on a Frozen Moon sur le site de la NASA">Voir l'image PIA08374: Inky Stains on a Frozen Moon sur le site de la NASA.</a></div>
PIA08374: Inky Stains on a Frozen Moon
<h1>PIA08375: The "Voyager" Mountains</h1><div class="PIA08375" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>Cassini zooms in, for the first time, on the patchy, bright and dark mountains originally identified in images from the NASA Voyager spacecraft taken more than 25 years earlier. The image was acquired during Cassini's only close flyby of Iapetus, a two-toned moon of Saturn.</p><p>The terrain seen here is located on the equator of Iapetus at approximately 199 degrees west longitude, in the transition region between the moon's bright and dark hemispheres. North is up.</p><p>The image was taken on Sept. 10, 2007, with the Cassini spacecraft narrow-angle camera at a distance of approximately 9,240 kilometers (5,740 miles) from Iapetus. Image scale is 55 meters (180 feet) per pixel.</p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.</p><p>For more information about the Cassini-Huygens mission visit <a href="http://saturn.jpl.nasa.gov">http://saturn.jpl.nasa.gov/home/index.cfm</a>. The Cassini imaging team homepage is at <a href="http://ciclops.org">http://ciclops.org</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA08375" onclick="window.open(this.href); return false;" title="Voir l'image PIA08375: The "Voyager" Mountains sur le site de la NASA">Voir l'image PIA08375: The "Voyager" Mountains sur le site de la NASA.</a></div>
PIA08375: The "Voyager" Mountains
<h1>PIA08376: Approaching Iapetus</h1><div class="PIA08376" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p>The slim crescent of Iapetus looms before the Cassini spacecraft as it approaches the mysterious moon.</p><p>Iapetus, 1,468 kilometers (912 miles) across, seen here in false color, is unique in its dramatic variation in brightness between the northern polar region and the middle and low latitudes. Equally prominent is the moon's equatorial ridge of towering mountains. The profile of the ridge against the darkness of space reveals that it is topped by a cratered plateau approximately 15 kilometers (9 miles) wide. Further west, the profile of the ridge changes from a long plateau to discrete peaks.</p><p>The mosaic consists of four image footprints across the surface of Iapetus and has a resolution of 489 meters (0.3 miles) per pixel.</p><p>A full-resolution clear filter image was combined with half-resolution images taken with infrared, green and ultraviolet spectral filters (centered at 752, 568 and 338 nanometers, respectively) to create this full-resolution false color mosaic. </p><p>The color seen in this view represents an expansion of the wavelength region of the electromagnetic spectrum visible to human eyes. The intense reddish-brown hue of the dark material is far less pronounced in true color images. The use of enhanced color makes the reddish character of the dark material more visible than it would be to the naked eye. In addition, the scene has been brightened to improve the visibility of surface features.</p><p>This view was acquired with the Cassini spacecraft narrow-angle camera on Sept. 10, 2007, at a distance of about 83,000 kilometers (51,600 miles) from Iapetus.</p><p></p><p>The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.</p><p>For more information about the Cassini-Huygens mission visit <a href="http://saturn.jpl.nasa.gov">http://saturn.jpl.nasa.gov/home/index.cfm</a>. The Cassini imaging team homepage is at <a href="http://ciclops.org">http://ciclops.org</a>.</p><br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA08376" onclick="window.open(this.href); return false;" title="Voir l'image PIA08376: Approaching Iapetus sur le site de la NASA">Voir l'image PIA08376: Approaching Iapetus sur le site de la NASA.</a></div>
PIA08376: Approaching Iapetus