Mars Global Surveyor Mars Orbiter Camera Release: MOC2-27A, -27B Mars Global Surveyor Mars Orbiter Camera Image ID: 568356409.8204 (P080-03)
(A) Excerpt from U. S. Geological Survey Mars Digital Image Mosaic (MDIM), reproduced at a scale of 230 meters/pixel. The outline of (B) is shown as a white box. Resolution in this image is 230 m (755 feet) per pixel (GIF = 315 KB).
(B) MOC image 8204 reproduced at a scale of 11.2 meters/pixel (1.4 MBytes GIF) or 5.6 meters/pixel full resolution (5.8 MBytes GIF).
CAPTIONThis picture shows materials that fill most of Ophir Chasma, one of the canyons of the central Valles Marineris. It was acquired on January 4, 1998 by the Mars Orbiter Camera (MOC), during the 82nd orbit around Mars of the Mars Global Surveyor spacecraft. At the top of the image is the floor of the chasm; the bottom of the image is as much as 4 km (2.5 miles) higher. Much of the relief between these two elevations occurs in the deeply channeled section in the upper one-half of the image.
The picture covers an area of 9.3 x 28 kilometers (5.8 x 17.4 miles), and features as small as 10 meters (about 30 feet) can be seen. The image is centered at 4.1°S, 72.2°W. At the bottom of the image, the surface displays many small, parallel ridges that are mostly likely sand dunes or large ripples. The interior of the chasm-fill material (exposed in the upper half of the image) appears to be of uniform brightness and resistance to erosion. Layering is only weakly expressed. Although dark layers and more competent layers are found elsewhere in the interior layered deposits, these deposits appear much more uniform. The erosional form of the channels suggests zones of slightly differing material strength substantially etched by the wind.
The origin of these deposits is not known. One theory proposes that they formed gradually in a set of giant lakes that filled the central canyons of Valles Marineris sometime in the past. Another hypothesis is that they are the result of enormous explosive volcanic eruptions. In either case, they were subsequently substantially eroded, although those processes are also subject to debate. Some argue that large amounts of water were needed to scour the materials away, while others contend that wind action and landslides are responsible for the features we see today. Detailed study of these MOC images may shed additional light on these competing theories, or we may need to wait for the images to be acquired by MOC during the mapping phase of the mission, which will be a factor of three higher in resolution.
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.
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