Mars Global Surveyor
Mars Orbiter Camera

Layered Material in West Arabia Terra Crater

MGS MOC Release No. MOC2-261, 4 December 2000


Context in Crater at 8°N 7°W

Subframe of Viking 1 orbiter image 829A43

(A) Dipping Toward Crater Center

"Colorized" subframe MOC M14-01647

(B) Layers and Dark Sand

"Colorized" subframe MOC M14-01647

(C) View Enhanced by Dark Sand

"Colorized" subframe MOC M14-01647

Hundreds of layers of similar thickness, texture, and pattern have been exposed by erosion in a 64 kilometer-wide (40 mile-wide) impact crater in western Arabia Terra at 8°N, 7°W. In other words, these layers provide a record of repeated, episodic changes that took place at some time far in the martian past, when this particular impact crater was the site of sediment deposition. Layers toward the center of the crater are nearly horizontal, but those closer to or draping over the crater walls are tilted (geologist use the term dipping) toward the basin center. These relationships suggest that the sediments that created these layers were deposited from above---perhaps by settling out of the martian atmosphere, or perhaps by settling out of water that might have occupied this crater as a lake.

The context view (top, left) was taken by the Viking 1 orbiter in 1978; in it, north is up and sunlight illuminates the scene from the right. The three Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) narrow angle (high resolution) views (A, B, C, above) sample layer outcrops that were previously not known to exist in this crater. Each MOC image is illuminated from the left. Dark material in Pictures B and C is windblown sand; in Picture C this sand enhances the appearance of the layers.

Additional Image Viewing Options:

Context in Crater at 8°N 7°W:

(A) Dipping Toward Crater Center:
(B) Layers and Dark Sand:
(C) View Enhanced by Dark Sand:

A brief description of how the color for the Narrow Angle (High Resolution) Images was generated:

The MOC narrow angle camera only takes grayscale (black and white) pictures. To create the color versions seen here, we have taken much lower resolution red and blue images acquired by the MOC's wide angle cameras, and by the Viking Orbiter cameras in the 1970s, synthesized a green image by averaging red and blue, and created a palette of colors that represent the range of colors on Mars. We then use a relationship that correlates color and brightness to assign a color to each gray level. This is only a crude approximation of martian color and should only be considered representative of Mars. It is likely the colors would not look like this to a human observer at Mars.

Images Credit: NASA/JPL/Malin Space Science Systems

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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