Mars Global Surveyor
Mars Orbiter Camera

MOC View of the Martian South Polar Residual Cap

MGS MOC Release No. MOC2-298, 6 December 2001

Martian South Polar Mesas and Pits in Frozen Carbon Dioxide

Small JPEG View (25% size) 555 KBytes
Medium JPEG View (50% size) 1.7 MBytes
Large JPEG View (100% original size) 5.6 MBytes

The portion of the martian south polar cap that persists through each southern hemisphere summer is known as the residual cap. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a 2.9 by 4.8 km (1.8 by 3 mi) area of the south polar residual cap as it appeared in mid-summer on 23 February 2000. The landscape of the south polar residual cap is dominated by layered, frozen carbon dioxide ("dry ice") that has been eroded into a variety of pits, troughs, buttes, and mesas. Commonly, the pits are circular and the mesa scarps are arcuate. In summer, as carbon dioxide is subliming away, the scarps bounding the pits and mesas darken. The darkened slopes may indicate that small amounts of dust are present, mixed-in with the ice. The ice is layered, indicating many cycles of deposition preceded the present period of sublimation and erosion. Recent MGS MOC images acquired in 2001 have indicated that the scarps are retreating an average of 3 meters (3.3 yards) per martian year. These findings, described in an accompanying release ("MOC Observes Changes in the South Polar Cap: Evidence for Recent Climate Change on Mars"), suggest that the martian climate may be changing today. As more carbon dioxide is released into the atmosphere each southern spring and summer, the atmospheric pressure of Mars may increase such that it could double in a few hundred to a thousand Mars years (687 Earth days = 1 Mars year). The picture shown here is from MOC image M12-02295 and is illuminated by sunlight from the lower right.

A version of this picture appears on the cover of the December 7, 2001, issue of Science and accompanies a paper regarding the MGS MOC discovery of evidence for martian climate change.

Other MOC Views of South Polar Terrain:

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

The MOC narrow angle camera only takes grayscale (black and white) pictures. To create the color picture seen here, we have taken much lower resolution red and blue images acquired by the MOC's wide angle cameras, 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 this vivid to a human observer at Mars.

Image 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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