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Subsection of Nirgal Vallis
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Subsection of Nirgal Vallis Image |
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This image is a subsection of the MGS Nirgal Vallis "B" image (PIA00942). 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. Nigral 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. 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. 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. Photo Credit: NASA/JPL/Malin Space Science Systems MRPS #84722 100297_7 605.crp, a subsection of 605.str/MOC212B 559303731.605 P006_05 |
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Rotated Perspective View of
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Rotated Perspective View of Nirgal Vallis |
| Description |
This is the full-resolution, rotated perspective image of Nirgal Vallis, a subset of PIA00942. Nigral 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. 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. 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. Photo Credit: NASA/JPL/Malin Space Science Systems MRPS #84704 100197_8 605.obl.sub.str/MOC212E 559303731.605 P006_05 |
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MGS Views of Nirgal Vallis
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MGS Views of Nirgal Vallis |
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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. Five images are shown above: (A) is an excerpt from the USGS MDIM, roughly 180 km (112 mile) square. The small box outlines the MOC image acquisition. (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. (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. (D) shows P006_05 skewed and rotated to the perspective that MOC was viewing at the time the image was taken. (E) shows a full-resolution version of a portion of the rotated perspective view. Nigral 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. 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. 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. Photo Credit: NASA/JPL/Malin Space Science Systems MRPS #84721 100297_2 605.all.str consisting of 605.ctx.str/MOC212A, 605.str/MOC212B, 605.sub.str/MOC212C, 605.obl.str/ MOC212D, and 605.obl.sub.str/MOC212E 559303731.605 P006_05 |
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Nirgal Vallis and its Windbl
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Nirgal Vallis and its Windblown Dunes |
| Description |
Nirgal Vallis is a narrow valley system that stretches approximately 420 kilometers (260 miles) across the martian surface near 28°S latitude, north of the large basin, Argyre. The floor of the valley system is largely covered with light-toned dunes and ripples. These windblown features obscure most of the original morphology of the valley floor. This view of a small portion of Nirgal Vallis was obtained by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) during Extended Mission subphase E02 on March 29, 2001. In each short tributary valley, dunes have a somewhat different orientation compared to those in the other valleys. The dune patterns here indicate that winds are locally controlled by the shape and orientation of each valley. The dunes just left of the center of the image have small craters on them, formed by meteor impact. The craters indicate that the dunes are not fresh, modern features, but are considerably older than they might at first seem. This image covers an area 3 km (1.9 mi) wide and is illuminated from the upper left. Image Credit: NASA/JPL/Malin Space Science Systems |
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