mgs_oct_pics_011105 Recently released images taken by the Mars Global Surveyor show the dynamic Martian terrain is anything but dull.
In the vast and varied plain of Utopia Planitia, an even more unusual field of sharply outlined pits attests to subterranean stresses. In September 1976, NASA's Viking 2 lander touched down on a rocky plain in Utopia Planitia near 48.0°N, 225.7°W. Nearly 1,700 kilometers (~1,060 miles) west of the Viking 2 site lies a pitted and fractured plain unlike anything found by the Mars Global Surveyor's Mars Orbiter Camera (MOC) elsewhere on Mars. Although the Martian northern plains are often considered to be "flat" or "featureless," the MOC has shown that, at the scale of a few tens of meters (tens of yards), these plains aren't at all "boring". In the October 2001 MOC image shown at right, a suite of sharply-outlined pits and fractures indicate that the upper surface materials are strong and indurated (cemented). The parallel and polygonal alignments of fractures and pits indicate that this area has been subjected to directional stress--perhaps weaker but not unlike the stresses in the Earth's crust that cause faulting and earthquakes. The pits furthermore indicate that something has been removed from beneath the rigid, upper crusted material. Unfortunately, the image does not provide obvious or direct answers as to what the rigid, indurated upper surface is made of, nor the composition of the material underneath it that was removed to cause the pitting. Some Mars scientists have speculated that removal of ground ice could cause the pitting, but whether this is actually the case is unknown and cannot be known with any certainty from the photograph alone.
| More upheaval is visible at several spots in the Ganges Chasma, a canyon at the East end of the vast Valles Marineris trough system, where steep walls, several kilometers high, have collapsed into the chasm, leaving enormous landslide deposits. The linear grooved and ridged pattern of the upper surface of the landslide results from shear, as the mass of rock and debris was moving across the landscape. When the landslide occurred, the debris was moving from the upper right toward the lower left. Dark sand dunes are banked up against the landslide deposit margins, indicating that considerable time has elapsed since the landslide occurred. |
One of the earliest results of the Mars Global Surveyor MOC investigation shortly after the spacecraft began to orbit Mars in 1997 was the discovery of layered rock outcrops reaching deep down into the Martian crust in the walls of the Valles Marineris. Since that time, thousands of MOC images have revealed layered rock in a variety of settings--crater floors, canyon interiors, and scarps exposed by faulting and pitting. One of the new MOC images shows the floor of an impact crater located near the equator in northwestern Schiaparelli Basin (0.15°N, 345.6°W). Layers of uniform thickness and appearance suggest that these materials are ancient sediments, possibly deposited in water or by wind. Wind has subsequently eroded and exposed the layers. Wind has also etched a lattice of undulating dunes into the floor of Herschel Crater, a 300-kilometer-wide impact basin located in the Martian southern cratered highlands, at 14.5°S, 230°W. The floor of this ancient crater exhibits patches of dark material which, when viewed by the high resolution Mars Orbiter Camera (MOC), resolve into fields of sand dunes. In detail, these dunes have a grooved, lineated surface. The grooves indicate that the dune sands are cemented together and have been eroded and scoured by wind. The age of the dunes and how their sands became cemented are unknown. These new photographs were released October 30, 2001 by Malin Space Science Systems, which has operated the Mars Global Surveyor's Mars Orbiter Camera (MOC) daily since the MGS mission began in 1999. The MOC actually consists of three cameras. One is a narrow-angle system that provides grayscale high-resolution views of the planet's surface (typically, 1.5 to 12 meters/pixel). The others are red and blue wide-angle cameras provide daily global weather monitoring, context images to determine where the narrow angle views were actually acquired, and regional coverage to monitor variable surface features such as polar frost and wind streaks. |
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Northern Plains of West Utopia: Parallel and polygonal alignments of fractures and pits indicate this area has been subjected to directional stress. Pits also indicate something has been removed from beneath the rigid, upper crusted material, possibly ground ice. Box, upper right, shows location.
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Schiaparelli Crater: Since MGS arrived at Mars in 1997, MOC images have revealed layered rock in a variety of settings. This spectacular example is found on the floor of an impact crater near the equator in northwestern Schiaparelli Basin.
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Herschel Crater: The floor of this ancient crater exhibits patches of dark material which, when viewed at high resolution, resolve into fields of sand dunes. In detail, these dunes have a grooved surface,indicating that the dune sands are cemented together and have been eroded and scoured by wind. The box,upper left, corner shows the location.
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Toe of Ganges Chasma Landslide: The grooved and ridged pattern of the upper surface results from shear. Dark sand dunes are banked up against the landslide deposit margins, indicating considerable time since the landslide occurred. The box at upper left shows the landslide location in Ganges Chasma.
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