Mission Mars Global Surveyor - 5

marswater_mgs_big.jpg
marswater_mgs_big.jpg
<h1>PIA00800: Medusae Fossae #1</h1><div class="PIA00800" lang="en" style="width:573px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">Extensive wind-swept plains of the Medusae Fossae formation on Mars. This northern subframe image, frame 3104, is of a 3.0 x 4.7 km area centered near 2.4 degrees north, 163.8 degrees west.<p>Figure caption from Science Magazine<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA00800" onclick="window.open(this.href); return false;" title="Voir l'image PIA00800: Medusae Fossae #1 sur le site de la NASA">Voir l'image PIA00800: Medusae Fossae #1 sur le site de la NASA.</a></div>
PIA00800: Medusae Fossae #1
<h1>PIA00801: Medusae Fossae #2</h1><div class="PIA00801" lang="en" style="width:573px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">Extensive wind-swept plains of the Medusae Fossae formation on Mars. This southern subframe image, frame 3104, is of a 3.0 x 4.7 km area centered near 2.0 degrees north, 163.8 degrees west.<p>Figure caption from Science Magazine<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA00801" onclick="window.open(this.href); return false;" title="Voir l'image PIA00801: Medusae Fossae #2 sur le site de la NASA">Voir l'image PIA00801: Medusae Fossae #2 sur le site de la NASA.</a></div>
PIA00801: Medusae Fossae #2
<h1>PIA00802: Hebes Chasma #1</h1><div class="PIA00802" lang="en" style="width:450px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">Complex variations in dune forms within Hebes Chasma. This northern subframe image, frame 3506, is a 2.3 x 3.6 km area centered near 0.6 degrees south, 76.3 degrees west.<p>Figure caption from Science Magazine<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA00802" onclick="window.open(this.href); return false;" title="Voir l'image PIA00802: Hebes Chasma #1 sur le site de la NASA">Voir l'image PIA00802: Hebes Chasma #1 sur le site de la NASA.</a></div>
PIA00802: Hebes Chasma #1
<h1>PIA00803: Hebes Chasma #2</h1><div class="PIA00803" lang="en" style="width:450px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">Complex variations in dune forms within Hebes Chasma. This southern subframe image, frame 3506, is a 2.3 x 3.6 km area centered near 0.8 degrees south, 76.3 degrees west<p>Figure caption from Science Magazine<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA00803" onclick="window.open(this.href); return false;" title="Voir l'image PIA00803: Hebes Chasma #2 sur le site de la NASA">Voir l'image PIA00803: Hebes Chasma #2 sur le site de la NASA.</a></div>
PIA00803: Hebes Chasma #2
<h1>PIA00804: Crommelin Crater #1</h1><div class="PIA00804" lang="en" style="width:645px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">Dunes in etch pits and troughs in Crommelin Crater in the Oxia Palus area. This 3.2 x 3.5 km image (frame 3001) is centered near 4.1 degrees north, 5.3 degrees west.<p>Figure caption from Science Magazine<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA00804" onclick="window.open(this.href); return false;" title="Voir l'image PIA00804: Crommelin Crater #1 sur le site de la NASA">Voir l'image PIA00804: Crommelin Crater #1 sur le site de la NASA.</a></div>
PIA00804: Crommelin Crater #1
<h1>PIA00805: Crommelin Crater #2</h1><div class="PIA00805" lang="en" style="width:645px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">Rare tear-shaped dark dunes in this 6.4 x 7.0 km image (frame 10004) centered near 47 degrees south, 341 degrees west.<p>Figure caption from Science Magazine<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA00805" onclick="window.open(this.href); return false;" title="Voir l'image PIA00805: Crommelin Crater #2 sur le site de la NASA">Voir l'image PIA00805: Crommelin Crater #2 sur le site de la NASA.</a></div>
PIA00805: Crommelin Crater #2
<h1>PIA00806: Tithonium Chasma/Ius Chasma</h1><div class="PIA00806" lang="en" style="width:477px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">Banded outcrops in walls of Tithonium Chasma/Ius Chasma section of Vallis Marineris. This 4.6 x 4.3 km image (frame 1303) is centered near 6.6 degrees south, 90.4 degrees west.<p>Figure caption from Science Magazine<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA00806" onclick="window.open(this.href); return false;" title="Voir l'image PIA00806: Tithonium Chasma/Ius Chasma sur le site de la NASA">Voir l'image PIA00806: Tithonium Chasma/Ius Chasma sur le site de la NASA.</a></div>
PIA00806: Tithonium Chasma/Ius Chasma
<h1>PIA00807: Candor Chasma</h1><div class="PIA00807" lang="en" style="width:477px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">Complex central deposits in the floor of the Candor Chasma section of Vallis Marineris. This 3.3 x 3.1 km image (frame 8405) is centered near 6.7 degrees south, 75.4 degrees west.<p>Figure caption from Science Magazine<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA00807" onclick="window.open(this.href); return false;" title="Voir l'image PIA00807: Candor Chasma sur le site de la NASA">Voir l'image PIA00807: Candor Chasma sur le site de la NASA.</a></div>
PIA00807: Candor Chasma
<h1>PIA00808: Ridges in Mars' south polar region</h1><div class="PIA00808" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">Complex of rectilinear intersecting ridges in the south polar region. This 20 x 14 km area image (frame 7908) is centered near 81.5 degrees south, 65 degrees west.<p>Figure caption from Science Magazine<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA00808" onclick="window.open(this.href); return false;" title="Voir l'image PIA00808: Ridges in Mars' south polar region sur le site de la NASA">Voir l'image PIA00808: Ridges in Mars' south polar region sur le site de la NASA.</a></div>
PIA00808: Ridges in Mars' south polar region
<h1>PIA00809: Textures in south polar ice cap #1</h1><div class="PIA00809" lang="en" style="width:592px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">Textures of the south polar permanent residual ice cap and polar layered terrains. This 30 x 29 km area image (frame 7709) is centered near 87 degrees south, 77 degrees west.<p>Figure caption from Science Magazine<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA00809" onclick="window.open(this.href); return false;" title="Voir l'image PIA00809: Textures in south polar ice cap #1 sur le site de la NASA">Voir l'image PIA00809: Textures in south polar ice cap #1 sur le site de la NASA.</a></div>
PIA00809: Textures in south polar ice cap #1
<h1>PIA00810: Textures in south polar ice cap #2</h1><div class="PIA00810" lang="en" style="width:592px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">Textures of the south polar permanent residual ice cap and polar layered terrains. This 15 x 14 km area image (frame 7306) is centered near 87 degrees south, 341 degrees west.<p>Figure caption from Science Magazine<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA00810" onclick="window.open(this.href); return false;" title="Voir l'image PIA00810: Textures in south polar ice cap #2 sur le site de la NASA">Voir l'image PIA00810: Textures in south polar ice cap #2 sur le site de la NASA.</a></div>
PIA00810: Textures in south polar ice cap #2
<h1>PIA00811: South polar region</h1><div class="PIA00811" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">Polar stereographic mosaic of the seasonal south polar region. Mars Orbiter Camera wide-angle red images from orbits 67 through 73<p>Figure caption from Science Magazine<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA00811" onclick="window.open(this.href); return false;" title="Voir l'image PIA00811: South polar region sur le site de la NASA">Voir l'image PIA00811: South polar region sur le site de la NASA.</a></div>
PIA00811: South polar region
<h1>PIA00941: MGS Views of Labyrinthus Noctis</h1><div class="PIA00941" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">MOC image P005_03 was acquired at 6:25 AM PDT on September 19, 1997, about 11 minutes after Mars Global Surveyor passed close to the planet for the fifth time. During the imaging period, the spacecraft was canted towards the sun-lit hemisphere by 25°, and the MOC was obliquely viewing features about 1600 km (1000 miles) away. The resolution at that distance was about 6 meters (20 feet) per picture element (pixels), but in order to improve the number of gray levels, the pixels were summed in both the cross-track and along-track directions, yielding final resolution of about 12 meters (40 feet) per pixel. The MOC image covers an area about 12 km X 12 km (7.5 X 7.5 miles).<p>Shown above are three pictures:<p> (A) is excepted from the U.S. Geological Survey's Mars Digital Image Mosaic, showing the Labyrinthus Noctis area west of the Valles Marineris. This image is about 175 km (109 miles) square. The outline of the MOC high resolution (Narrow Angle) camera image is centered at 4.6°S, 102.6°W.<p>(B) is the MOC frame P005_03. Because the MOC acquires its images one line at a time, the cant angle towards the sun-lit portion of the planet, the spacecraft orbital velocity, and the spacecraft rotational velocity combined to distort the image slightly.<p>(C) shows P005_03 skewed and rotated to the perspective that MOC was viewing at the time the image was taken.<p> Labyrinthus Noctis is near the crest of a large (many thousands of kilometers) upcoming of the Martian crust, and the 2000 meter (6500 foot) deep canyons visible in these pictures are bounded by faults. Debris shed from the steep slopes has moved down into after the canyons opened. Small dunes are seen in the lowest area, beneath the high cliffs.<p>Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The spacecraft has been using atmospheric drag to reduce the size of its orbit for the past three weeks, and will achieve a circular orbit only 400 km (248 mi) above the surface early next year. Mapping operations begin in March 1998. At that time, MOC narrow angle images will be 5-10 times higher resolution than these pictures.<p>Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA00941" onclick="window.open(this.href); return false;" title="Voir l'image PIA00941: MGS Views of Labyrinthus Noctis sur le site de la NASA">Voir l'image PIA00941: MGS Views of Labyrinthus Noctis sur le site de la NASA.</a></div>
PIA00941: MGS Views of Labyrinthus Noctis
<h1>PIA00942: MGS Views of Nirgal Vallis</h1><div class="PIA00942" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">At 3:08:30 AM on September 21, 1997, the MOC field of view swept across the highland valley network Nirgal Vallis at 28.5°S, 41.6 W. Although the MGS spacecraft was at an altitude of about 400 km (250 miles), the MOC was pointed obliquely across the planet at about 35°, so the distance to Nirgal Vallis was closer to 800 km (500 miles). At that range and viewing angle, the MOC field of view was about 16 km (10 miles) wide, and the resolution was about 9 meters (30 feet) per pixel. The acquired image is 36 km (23 miles) long.<p>Five images are shown above:<p> (A) is an excerpt from the USGS MDIM, roughly 180 km (112 mile) square. The small box outlines the MOC image acquisition.<p>(B) is MOC frame P006_05, shown here at reduced resolution because the full image is almost 7 MBytes in size. Because the MOC acquires its images one line at a time, the cant angle towards the sun-lit portion of the planet, the spacecraft orbital velocity, and the spacecraft rotational velocity combined to significantly distort the image. However, even in this reduced resolution version, dunes can be seen in the canyon and in areas on the upland surface around the canyon.<p>(C) shows a portion of P006_05 at the full resolution of the data. This view shows the dunes more clearly, and also illustrates better the distortion introduced by the method of data acquisition.<p>(D) shows P006_05 skewed and rotated to the perspective that MOC was viewing at the time the image was taken.<p>(E) shows a full-resolution version of a portion of the rotated perspective view.<p> Nirgal Vallis is one of a number of canyons called valley networks or runoff channels. Much of the debate concerning the origin of these valleys centers on whether they were formed by water flowing across the surface, or by collapse and upslope erosion associated with groundwater processes. At the resolution of this image, it is just barely possible to discern an interwoven pattern of lines on the highland surrounding the valley, but it is not possible to tell whether this is a pattern of surficial debris (sand or dust), as might be expected with the amount of crater burial seen, or a pattern of drainage channels. With 4X better resolution from its mapping orbit, MOC should easily be able to tell the difference between these two possibilities.<p>Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The spacecraft has been using atmospheric drag to reduce the size of its orbit for the past three weeks, and will achieve a circular orbit only 400 km (248 mi) above the surface early next year. Mapping operations begin in March 1998. At that time, MOC narrow angle images will be 5-10 times higher resolution than these pictures.<p>Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA00942" onclick="window.open(this.href); return false;" title="Voir l'image PIA00942: MGS Views of Nirgal Vallis sur le site de la NASA">Voir l'image PIA00942: MGS Views of Nirgal Vallis sur le site de la NASA.</a></div>
PIA00942: MGS Views of Nirgal Vallis
<h1>PIA00943: Subsection of Nirgal Vallis Image</h1><div class="PIA00943" lang="en" style="width:630px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">This image is a subsection of the MGS Nirgal Vallis "B" image (PIA00942).<p>This subsection of frame P006_05 is shown here at reduced resolution because the full image is almost 7 MBytes in size. Because the MOC acquires its images one line at a time, the cant angle towards the sun-lit portion of the planet, the spacecraft orbital velocity, and the spacecraft rotational velocity combined to significantly distort the image. However, even in this reduced resolution version, dunes can be seen in the canyon and in areas on the upland surface around the canyon.<p>Nirgal Vallis is one of a number of canyons called valley networks or runoff channels. Much of the debate concerning the origin of these valleys centers on whether they were formed by water flowing across the surface, or by collapse and upslope erosion associated with groundwater processes. At the resolution of this image, it is just barely possible to discern an interwoven pattern of lines on the highland surrounding the valley, but it is not possible to tell whether this is a pattern of surficial debris (sand or dust), as might be expected with the amount of crater burial seen, or a pattern of drainage channels. With 4X better resolution from its mapping orbit, MOC should easily be able to tell the difference between these two possibilities.<p>Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The spacecraft has been using atmospheric drag to reduce the size of its orbit for the past three weeks, and will achieve a circular orbit only 400 km (248 mi) above the surface early next year. Mapping operations begin in March 1998. At that time, MOC narrow angle images will be 5-10 times higher resolution than these pictures.<p>Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA00943" onclick="window.open(this.href); return false;" title="Voir l'image PIA00943: Subsection of Nirgal Vallis Image sur le site de la NASA">Voir l'image PIA00943: Subsection of Nirgal Vallis Image sur le site de la NASA.</a></div>
PIA00943: Subsection of Nirgal Vallis Image
<h1>PIA00944: Rotated Perspective View of Nirgal Vallis</h1><div class="PIA00944" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">This is the full-resolution, rotated perspective image of Nirgal Vallis, a subset of PIA00942. Nirgal Vallis is one of a number of canyons called valley networks or runoff channels. Much of the debate concerning the origin of these valleys centers on whether they were formed by water flowing across the surface, or by collapse and upslope erosion associated with groundwater processes. At the resolution of this image, it is just barely possible to discern an interwoven pattern of lines on the highland surrounding the valley, but it is not possible to tell whether this is a pattern of surficial debris (sand or dust), as might be expected with the amount of crater burial seen, or a pattern of drainage channels. With 4X better resolution from its mapping orbit, MOC should easily be able to tell the difference between these two possibilities.<p>Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The spacecraft has been using atmospheric drag to reduce the size of its orbit for the past three weeks, and will achieve a circular orbit only 400 km (248 mi) above the surface early next year. Mapping operations begin in March 1998. At that time, MOC narrow angle images will be 5-10 times higher resolution than these pictures.<p>Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA00944" onclick="window.open(this.href); return false;" title="Voir l'image PIA00944: Rotated Perspective View of Nirgal Vallis sur le site de la NASA">Voir l'image PIA00944: Rotated Perspective View of Nirgal Vallis sur le site de la NASA.</a></div>
PIA00944: Rotated Perspective View of Nirgal Vallis
<h1>PIA00945: MGS Views of Labyrinthus Noctis</h1><div class="PIA00945" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">This is MOC frame P005_03, a subset of PIA00941. MOC image P005_03 was acquired at 6:25 AM PDT on September 19, 1997, about 11 minutes after Mars Global Surveyor passed close to the planet for the fifth time. During the imaging period, the spacecraft was canted towards the sunlit hemisphere by 25°, and the MOC was obliquely viewing features about 1600 km (1000 miles) away. The resolution at that distance was about 6 meters (20 feet) per picture element (pixels), but in order to improve the number of gray levels, the pixels were summed in both the cross-track and along-track directions, yielding final resolution of about 12 meters (40 feet) per pixel. The MOC image covers an area about 12 km X 12 km (7.5 X 7.5 miles).<p>Labyrinthus Noctis near the crest of a large (many thousands of kilometers) upcoming of the Martian crust, and the 2000 meter (6500 foot) deep canyons visible in these pictures are bounded by faults. Debris shed from the steep slopes has moved down into after the canyons opened. Small dunes are seen in the lowest area, beneath the high cliffs.<p>Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The spacecraft has been using atmospheric drag to reduce the size of its orbit for the past three weeks, and will achieve a circular orbit only 400 km (248 mi) above the surface early next year. Mapping operations begin in March 1998. At that time, MOC narrow angle images will be 5-10 times higher resolution than these pictures.<p>Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA00945" onclick="window.open(this.href); return false;" title="Voir l'image PIA00945: MGS Views of Labyrinthus Noctis sur le site de la NASA">Voir l'image PIA00945: MGS Views of Labyrinthus Noctis sur le site de la NASA.</a></div>
PIA00945: MGS Views of Labyrinthus Noctis
<h1>PIA01021: Western Tithonium Chasma/Ius Chasma, Valles Marineris</h1><div class="PIA01021" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">On October 3, 1997, the MOC acquired this image of the western Tithonium Chasma/Ius Chasma portion of the Valles Marineris, centered at 6.6°S, 90.4°W, at 1:16 PM PDT. Although the lighting beneath the spacecraft was very poor, the camera was canted towards the sun, and the illumination was equivalent to roughly 5 PM local time (the sun was about 17° above the horizon). In the image, the canyon floors are mostly shadowed, but steep slopes in the area are exquisitely highlighted.<p>The area outlined in the upper right image, the highest resolution view of the region previously available, is 6.6 km (4 miles) wide by 55.6 km (34.5 miles) long. The ridges to the north and south are about 4000 m (13,000 feet) above the floor of the troughs, but in the area photographed, the relief is slightly lower (about 3000 m, or 10,000 feet). The top portion of the image is shown on the left, and a section of that image is shown enlarged at lower right. The scale is 6.45 m/pixel across the image by 9.65 m/pixel down the image. The left and lower right images are available at higher resolution as PIA01022 and PIA01023, respectively.<p>Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The original mission plan called for using friction with the planet's atmosphere to reduce the orbital energy, leading to a two-year mapping mission from close, circular orbit (beginning in March 1998). Owing to difficulties with one of the two solar panels, aerobraking was suspended in mid-October and resumed in November 8. Many of the original objectives of the mission, and in particular those of the camera, are likely to be accomplished as the mission progresses.<p>Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA01021" onclick="window.open(this.href); return false;" title="Voir l'image PIA01021: Western Tithonium Chasma/Ius Chasma, Valles Marineris sur le site de la NASA">Voir l'image PIA01021: Western Tithonium Chasma/Ius Chasma, Valles Marineris sur le site de la NASA.</a></div>
PIA01021: Western Tithonium Chasma/Ius Chasma, Valles Marineris
<h1>PIA01022: Western Tithonium Chasma/Ius Chasma, Valles Marineris - High Resolution Image</h1><div class="PIA01022" lang="en" style="width:711px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">Most remarkable about this MOC image is the discovery of light and dark layers in the rock outcrops of the canyon walls. In the notable, triangular mountain face (at center), some 80 layers, typically alternating in brightness and varying in thickness from 5 to 50 meters (16 to 160 feet), are clearly visible. This shear mountain cliff, over 1000 m (3200 ft) tall, is only one of several outcrops that, together, indicate layering almost the entire depth of the canyon.<p>This type of bedrock layering has never been seen before in Valles Marineris. It calls into question common views about the upper crust of Mars, for example, that there is a deep layer of rubble underlying most of the martian surface, and argues for a much more complex early history for the planet.<p>Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The original mission plan called for using friction with the planet's atmosphere to reduce the orbital energy, leading to a two-year mapping mission from close, circular orbit (beginning in March 1998). Owing to difficulties with one of the two solar panels, aerobraking was suspended in mid-October and resumed in November 8. Many of the original objectives of the mission, and in particular those of the camera, are likely to be accomplished as the mission progresses.<p>Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA01022" onclick="window.open(this.href); return false;" title="Voir l'image PIA01022: Western Tithonium Chasma/Ius Chasma, Valles Marineris - High Resolution Image sur le site de la NASA">Voir l'image PIA01022: Western Tithonium Chasma/Ius Chasma, Valles Marineris - High Resolution Image sur le site de la NASA.</a></div>
PIA01022: Western Tithonium Chasma/Ius Chasma, Valles Marineris - High Resolution Image
<h1>PIA01023: Western Tithonium Chasma/Ius Chasma, Valles Marineris - High Resolution Image</h1><div class="PIA01023" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">Most remarkable about this MOC image is the discovery of light and dark layers in the rock outcrops of the canyon walls. In the notable, triangular mountain face (at center), some 80 layers, typically alternating in brightness and varying in thickness from 5 to 50 meters (16 to 160 feet), are clearly visible. This shear mountain cliff, over 1000 m (3200 ft) tall, is only one of several outcrops that, together, indicate layering almost the entire depth of the canyon.<p>This type of bedrock layering has never been seen before in Valles Marineris. It calls into question common views about the upper crust of Mars, for example, that there is a deep layer of rubble underlying most of the martian surface, and argues for a much more complex early history for the planet.<p>Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The original mission plan called for using friction with the planet's atmosphere to reduce the orbital energy, leading to a two-year mapping mission from close, circular orbit (beginning in March 1998). Owing to difficulties with one of the two solar panels, aerobraking was suspended in mid-October and resumed in November 8. Many of the original objectives of the mission, and in particular those of the camera, are likely to be accomplished as the mission progresses.<p>Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA01023" onclick="window.open(this.href); return false;" title="Voir l'image PIA01023: Western Tithonium Chasma/Ius Chasma, Valles Marineris - High Resolution Image sur le site de la NASA">Voir l'image PIA01023: Western Tithonium Chasma/Ius Chasma, Valles Marineris - High Resolution Image sur le site de la NASA.</a></div>
PIA01023: Western Tithonium Chasma/Ius Chasma, Valles Marineris - High Resolution Image
<h1>PIA01024: Valley and Surrounding Terrain Adjacent to Schiaparelli Crater</h1><div class="PIA01024" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">This view of Mars, showing a small area immediately south of the large crater Schiaparelli, was taken by the Mars Orbiter Camera during its 23rd pass close to the planet. It was acquired on October 18, 1997, at 3:42 PM PST, about 10 minutes after closest approach. The image covers an area 4.6 km (2.9 miles) wide by 21.1 km (13.1 miles) high, at a resolution of 4.5 m by 7.9 m (14.75 X 25.9 feet) per picture element, and is centered at 5.5°S, 340.7°W. The local time of the acquisition was about 4:50 PM.<p>The image at left shows the location in the best available image from the Viking Orbiters (approximately 240 m/pixel). The center image is the full image, while at right is an enlarged portion of it. The two right images are available at higher resolution as PIA01025 and PIA01026, respectively.<p>Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The original mission plan called for using friction with the planet's atmosphere to reduce the orbital energy, leading to a two-year mapping mission from close, circular orbit (beginning in March 1998). Owing to difficulties with one of the two solar panels, aerobraking was suspended in mid-October and resumed in November 8. Many of the original objectives of the mission, and in particular those of the camera, are likely to be accomplished as the mission progresses.<p>Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA01024" onclick="window.open(this.href); return false;" title="Voir l'image PIA01024: Valley and Surrounding Terrain Adjacent to Schiaparelli Crater sur le site de la NASA">Voir l'image PIA01024: Valley and Surrounding Terrain Adjacent to Schiaparelli Crater sur le site de la NASA.</a></div>
PIA01024: Valley and Surrounding Terrain Adjacent to Schiaparelli Crater
<h1>PIA01025: Valley and Surrounding Terrain Adjacent to Schiaparelli Crater - High Resolution Image</h1><div class="PIA01025" lang="en" style="width:457px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">There are two exciting results seen in this image. First, the small dunes moving from left to right (north to south) along the canyon floor are apparently derived from bright deposits within Schiaparelli crater. They are brighter than most martian dunes and may represent a unique composition. The shape of the dunes, and their relationships to one another, strongly suggest that these dunes have been active recently, although whether that means within the past year or the past century cannot be told from these images alone.<p>The second discovery made in this image are the small depressions found in the upper left and center of image (best seen in PIA01026) with faint dark lines crossing lighter floors. These depressions, and the pattern of lines, are similar to dry lake beds seen throughout the deserts of the southwestern United States. The light material may be salts or other minerals deposited as the lake evaporated, and the dark lines may be cracks created as the material dried out. Alternative explanations for the dark lines, involving freezing and thawing of water-saturated soil, are equally intriguing. In both cases, these features are the examples of a suite of such forms that can be used to diagnose the amount and distribution of surficial water that may have once ponded on Mars.<p>Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The original mission plan called for using friction with the planet's atmosphere to reduce the orbital energy, leading to a two-year mapping mission from close, circular orbit (beginning in March 1998). Owing to difficulties with one of the two solar panels, aerobraking was suspended in mid-October and resumed in November 8. Many of the original objectives of the mission, and in particular those of the camera, are likely to be accomplished as the mission progresses.<p>Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA01025" onclick="window.open(this.href); return false;" title="Voir l'image PIA01025: Valley and Surrounding Terrain Adjacent to Schiaparelli Crater - High Resolution Image sur le site de la NASA">Voir l'image PIA01025: Valley and Surrounding Terrain Adjacent to Schiaparelli Crater - High Resolution Image sur le site de la NASA.</a></div>
PIA01025: Valley and Surrounding Terrain Adjacent to Schiaparelli Crater - High Resolution Image
<h1>PIA01027: Complex Floor Deposits Within Western Ganges Chasma, Valles Marineris</h1><div class="PIA01027" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">On October 26, 1997, MOC took this image of Mars 10 minutes after its closest approach to the planet (1:46 AM PST). The view shows the floor of western Ganges Chasma (7.8°S 51.8°W), covering an area 2.6 km (1.6 miles) wide by 45.4 km (28.2 miles) long at a resolution of 5 by 7.4 meters (16.4 by 24.3 feet) per picture element. The local time on Mars when the picture was taken was 4:35 PM.<p>The center image (available at higher resolution as PIA01028) shows the northern portion of the area inscribed in the left image. The right image (PIA01029) shows the southern portion.<p>Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The original mission plan called for using friction with the planet's atmosphere to reduce the orbital energy, leading to a two-year mapping mission from close, circular orbit (beginning in March 1998). Owing to difficulties with one of the two solar panels, aerobraking was suspended in mid-October and resumed in November 8. Many of the original objectives of the mission, and in particular those of the camera, are likely to be accomplished as the mission progresses.<p>Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA01027" onclick="window.open(this.href); return false;" title="Voir l'image PIA01027: Complex Floor Deposits Within Western Ganges Chasma, Valles Marineris sur le site de la NASA">Voir l'image PIA01027: Complex Floor Deposits Within Western Ganges Chasma, Valles Marineris sur le site de la NASA.</a></div>
PIA01027: Complex Floor Deposits Within Western Ganges Chasma, Valles Marineris
<h1>PIA01028: Complex Floor Deposits Within Western Ganges Chasma, Valles Marineris - High Resolution Image</h1><div class="PIA01028" lang="en" style="width:480px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">This image shows the area near the canyon wall, where large blocks of the upland surface have slumped down into the canyon. Close inspection of this image shows numerous small dark dots that are in fact individual rocks on the surface of Mars. These rocks vary from the size of a small automobile to the size of a house, have fallen down steep slopes.<p>Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The original mission plan called for using friction with the planet's atmosphere to reduce the orbital energy, leading to a two-year mapping mission from close, circular orbit (beginning in March 1998). Owing to difficulties with one of the two solar panels, aerobraking was suspended in mid-October and resumed in November 8. Many of the original objectives of the mission, and in particular those of the camera, are likely to be accomplished as the mission progresses.<p>Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA01028" onclick="window.open(this.href); return false;" title="Voir l'image PIA01028: Complex Floor Deposits Within Western Ganges Chasma, Valles Marineris - High Resolution Image sur le site de la NASA">Voir l'image PIA01028: Complex Floor Deposits Within Western Ganges Chasma, Valles Marineris - High Resolution Image sur le site de la NASA.</a></div>
PIA01028: Complex Floor Deposits Within Western Ganges Chasma, Valles Marineris - High Resolution Image
<h1>PIA01029: Complex Floor Deposits Within Western Ganges Chasma, Valles Marineris - High Resolution Image</h1><div class="PIA01029" lang="en" style="width:480px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">This image shows a remarkable landscape of ridges and troughs that very closely resemble folded and warped sediments on Earth. This is the first time such warped beds have been seen on Mars, and neither their origin nor their occurrence within Ganges Chasma is understood. It is possible these are beds folded by a large landslide, but that would be very unusual. Alternatively, these may be folded sedimentary beds, similar to horizontal beds seen elsewhere in Ganges Chasma. However, what forces then folded these particular beds while leaving the others undeformed is unknown. Future imaging within this and the other Valles Marineris will be used to address such issues.<p>Launched on November 7, 1996, Mars Global Surveyor entered Mars orbit on Thursday, September 11, 1997. The original mission plan called for using friction with the planet's atmosphere to reduce the orbital energy, leading to a two-year mapping mission from close, circular orbit (beginning in March 1998). Owing to difficulties with one of the two solar panels, aerobraking was suspended in mid-October and resumed in November 8. Many of the original objectives of the mission, and in particular those of the camera, are likely to be accomplished as the mission progresses.<p>Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA01029" onclick="window.open(this.href); return false;" title="Voir l'image PIA01029: Complex Floor Deposits Within Western Ganges Chasma, Valles Marineris - High Resolution Image sur le site de la NASA">Voir l'image PIA01029: Complex Floor Deposits Within Western Ganges Chasma, Valles Marineris - High Resolution Image sur le site de la NASA.</a></div>
PIA01029: Complex Floor Deposits Within Western Ganges Chasma, Valles Marineris - High Resolution Image
<h1>PIA01032: Evidence for Recent Liquid Water on Mars:"Weeping" Layer in Gorgonum Chaos</h1><div class="PIA01032" lang="en" style="width:712px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><a href="/figures/moc2_235b.gif"></a><p>This image, acquired by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) in May 2000 shows numerous examples of martian gullies that all start--or head--in a specific layer roughly a hundred meters beneath the surface of Mars. These features are located on the south-facing wall of a trough in the Gorgonum Chaos region, an area found to have many examples of gullies proposed to have formed by seepage and runoff of liquid water in recent martian times.<p>The layer from which the gullies emanate has recessed backward to form an overhang beneath a harder layer of rock. The larger gullies have formed an alcove--an area above the overhang from which debris has collapsed to leave a dark-toned scar. Below the layer of seepage is found a dark, narrow channel that runs down the slope to an apron of debris. The small, bright, parallel features at the base of the cliff at the center-right of the picture is a series of large windblown ripples.<p>Although the dark tone of the alcoves and channels in this image is not likely to be the result of wet ground (the contrast in this image has been enhanced), it does suggest that water has seeped out of the ground and moved down the slope quite recently. Sharp contrasts between dark and light areas are hard to maintain on Mars for very long periods of time because dust tends to coat surfaces and reduce brightness differences. To keep dust from settling on a surface, it has to have undergone some process of erosion (wind, landslides, water runoff) relatively recently. There is no way to know how recent this activity was, but educated guesses center between a few to tens of years, and it is entirely possible that the area shown in this image has water seeping out of the ground today.<p>Centered near 37.9°S, 170.2°W, sunlight illuminates the MOC image from the upper left, north is toward the upper right. The context view above is from the Viking 1 orbiter and was acquired in 1977. The Viking picture is illuminated from the upper right; north is up. The small white box in the context frame shows the location of the high resolution MOC view.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA01032" onclick="window.open(this.href); return false;" title="Voir l'image PIA01032: Evidence for Recent Liquid Water on Mars:"Weeping" Layer in Gorgonum Chaos sur le site de la NASA">Voir l'image PIA01032: Evidence for Recent Liquid Water on Mars:"Weeping" Layer in Gorgonum Chaos sur le site de la NASA.</a></div>
PIA01032: Evidence for Recent Liquid Water on Mars:"Weeping" Layer in Gorgonum Chaos
<h1>PIA01034: Evidence for Recent Liquid Water on Mars: Gullies at 70°S in Polar Pit Walls</h1><div class="PIA01034" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><p><a href="/figures/moc2_237b.gif"></a><p>Gully landforms proposed to have been caused by geologically-recent seepage and runoff of liquid water on Mars are found in the most unlikely places. They typically occur in areas that are quite cold--well below freezing--all year round. Like the old adage about moss on trees, nearly all of them form on slopes that face away from sunlight. Most of the gullies occur at latitudes between 30° and 70°.<p>The highest latitude at which martian gullies have been found is around 70°-75°S on the walls of pits developed in the south polar pitted plains. If you were at this same latitude on Earth, you would be in Antarctica. This region spends much of the winter--which lasts approximately 6 months on Mars--in darkness and at temperatures cold enough to freeze carbon dioxide (around -130°C or -200°F). Nevertheless, gullies with very sharp, deep, v-shaped channels are seen on the pit walls (above, left).<p>Based upon the locations of the tops of the channels on the slope shown here, the inferred site of liquid seepage is located at a layer in the pit wall about 1/3 of the way down from the top of the MOC image. The channels start wide and taper downslope. The area above the channels is layered and has been eroded by mass movement--dry avalanching of debris--to form a pattern of chutes and ridges on the upper slope of the pit wall. The top layer appears to have many boulders in it (each about the size of a small house), these boulders are left behind on the upper slopes of the pit wall as debris is removed.<p>Centered near 70.7°S, 355.7°W, the MOC image was acquired July 14, 1999, and covers an area approximately 2.8 km (1.7 mi) wide by 2.1 km (1.3 mi) high. Sunlight illuminates the MOC image from the upper left and north is toward the upper left. The context view (right) is from the Viking 2 orbiter and was acquired in 1977. The Viking picture is illuminated from the top/upper left; north is toward the upper right. The small white box in the context frame (upper right corner) shows the location of the high resolution MOC view.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA01034" onclick="window.open(this.href); return false;" title="Voir l'image PIA01034: Evidence for Recent Liquid Water on Mars: Gullies at 70°S in Polar Pit Walls sur le site de la NASA">Voir l'image PIA01034: Evidence for Recent Liquid Water on Mars: Gullies at 70°S in Polar Pit Walls sur le site de la NASA.</a></div>
PIA01034: Evidence for Recent Liquid Water on Mars: Gullies at 70°S in Polar Pit Walls
<h1>PIA01036: Evidence for Recent Liquid Water on Mars: Seepage Sites in "Aerobraking Crater" Revisited</h1><div class="PIA01036" lang="en" style="width:800px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;">(A)<br><a href="/figures/moc2_239a.gif"></a>(B)<br><a href="/figures/moc2_239b.gif"></a>(C)<br><a href="/figures/moc2_239d.gif"><a>(D)<br><br>You will need 3D glasses to view this anaglyph<p>The first clue that there might be places on Mars where liquid groundwater seeps out onto the surface came from a picture taken by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) during the pre-mapping Orbit Insertion Phase of the mission. The picture, shown in (A) above, was taken at the end of December 1997 while the spacecraft was still in the midst of aerobraking maneuvers to put it into the circular orbit needed for the Mapping Phase of the project. The Aerobraking 1 image, AB1-07707, showed dark, v-shaped scars on the western wall of a 50 kilometer-(31 mile)-diameter impact crater in southern Noachis Terra at 65°S, 15°W (see B, above, for context). The v-shaped features taper downslope to form narrow, somewhat curved channels. The relationship seen here was interpreted by MOC scientists to be similar to seepage landforms on Earth that form where springs emerge on a slope and water runs downhill.<p>Once MGS achieved its Mapping Orbit in March 1999, the MOC was in a better position to take pictures of 10 times higher resolution than the Aerobraking AB1-07707 image. The opportunity to take a new picture of the proposed "seepage" sites on the wall of the crater in southern Noachis finally arose in January 2000. The result is MOC image M11-00530, shown above in (top) and (C). This new close-up shows that the darkly-shaped scars host many small channels of only a few meters (yards) across. These small channels run downslope and coalesce at the apex (or point) of each "v." Amid the small channels are many large boulders, some of them the size of houses, that have eroded out of the crater wall. A 3-D view created using the AB1 and M11 images is shown in (D). The stereo picture (red-blue "3D" glasses required) emphasizes the presence of small channels and valleys, and shows that these valleys start almost at the very top of the v-shaped dark areas.<p>The context picture in (B) is a mosaic of Viking 2 orbiter images 497B47 and 497B48 acquired December 28, 1977. The Aerobraking MGS MOC image, AB1-07707, is shown overlain on the Viking context image; it was taken 20 years later on December 29, 1997. The smaller white box in the context picture shows the location of MOC Mapping Phase image M11-00530, roughly 2 years later on January 4, 2000. North is "up" in pictures (A) and (B), and to the lower right in (top), (C), and (D). Sunlight illuminates (A) from the upper left, (B) from the upper right, and (top) and (C) from the upper right. The top image in (top) is the aerobraking image, AB1-07707, with a white box indicating the location of the lower image, M11-00530, and the stereo pair in (D). The white box on the left in (C) shows the location of the close-up on the right in (C).<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA01036" onclick="window.open(this.href); return false;" title="Voir l'image PIA01036: Evidence for Recent Liquid Water on Mars: Seepage Sites in "Aerobraking Crater" Revisited sur le site de la NASA">Voir l'image PIA01036: Evidence for Recent Liquid Water on Mars: Seepage Sites in "Aerobraking Crater" Revisited sur le site de la NASA.</a></div>
PIA01036: Evidence for Recent Liquid Water on Mars: Seepage Sites in "Aerobraking Crater" Revisited
<h1>PIA01037: Evidence for Recent Liquid Water on Mars: South-facing Walls of Nirgal Vallis</h1><div class="PIA01037" lang="en" style="width:627px;text-align:left;margin:auto;background-color:#000;padding:10px;max-height:150px;overflow:auto;"><a href="/figures/moc2_240b.gif"></a><br><p>Nirgal Vallis is an ancient valley thought for nearly 3 decades to have been carved, in part, by running water at some time far back in the martian past. Today the valley is, like the rest of Mars, quite dry. However, some of the high resolution Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images reveal small gullies on the walls of this valley system. An example is shown here (above, left), in which more than 14 channels nearly 1 kilometer (0.6 miles) long run down the south-facing slope of the Nirgal Vallis wall. Each narrow channel starts at about the same position below the top of the valley wall, indicating that there is a layer along which a liquid--most likely, water--has percolated until it reached the cliff, then ran down hill to form the channels and the fan-shaped aprons at the bottom of the slope. Some of the apron deposits seem to cover the dunes on the floor of the valley (lower 1/3 of the image), suggesting that the channels and aprons formed more recently than the dunes. The fact that neither the dunes nor the aprons and channels have impact craters on them suggests that these features are all geologically young, meaning a few million years at most, a few days or weeks at least.<p>Nirgal Vallis is the one location where martian gullies thought to be related to recent groundwater seepage have been found closer to the equator than 30° latitude. All of the features in Nirgal, however, occur close to 30°--they are all between 27°S and 30°S. The MOC image is near 29.7°S, 38.6°W, and was obtained July 12, 1999. The MOC picture covers an area approximately 2.3 km (1.4 mi) wide by 2.8 km (1.7 mi) long. Sunlight illuminates the MOC scene from the upper left, and north is up. The context view (right) is a mosaic of Viking orbiter images illuminated from the upper right from the U.S. Geological Survey Mars Digital Mosaic maps. The small white box in the context frame (just below center of image) shows the location of the high resolution MOC view.<p>It is ironic to note that <a href="/catalog/PIA00942">one of the first pictures returned to Earth from MOC</a>, back on September 21, 1997, showed similar small channels and aprons on the wall of Nirgal Vallis--but their significance was not realized at the time.<br /><br /><a href="http://photojournal.jpl.nasa.gov/catalog/PIA01037" onclick="window.open(this.href); return false;" title="Voir l'image PIA01037: Evidence for Recent Liquid Water on Mars: South-facing Walls of Nirgal Vallis sur le site de la NASA">Voir l'image PIA01037: Evidence for Recent Liquid Water on Mars: South-facing Walls of Nirgal Vallis sur le site de la NASA.</a></div>
PIA01037: Evidence for Recent Liquid Water on Mars: South-facing Walls of Nirgal Vallis

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