Mars Global Surveyor Mars Orbiter Camera Release: MOC2-36A, -36B, -36C, -36D Mars Global Surveyor Mars Orbiter Camera Image ID: 567897744.7709 P077-09
CAPTIONTextures on the surface of the permanent south polar ice cap are visible in this MOC image taken in late southern spring. The Mariner 9 (C) and Viking (A & B) images show what this area would look like in summer--the large diagonal lineation that has a curved "hook" at the lower right of the MOC subframe is defrosted in the summertime views from Viking and Mariner 9. The MOC frame, however, was taken at a time when it was still cold enough that the region, including this lineation, is covered with ice and snow. The south polar cap on Mars is known from previous study to contain a mixture of water ice, frozen carbon dioxide ("dry ice") and dust. Typical temperatures here are as low as -125°C (-193°F) or more.
The rough and pitted textures on this portion of the polar cap are probably caused by a combination of factors: (a) the removal of ice in the spring and summer seasons, (b) wind erosion, and (c) removal and/or erosion of ice and dust over long time periods (millions of years). When the ice cap warms in spring and summer, it does not melt. Instead, the ice (water and carbon dioxide) changes directly from solid to gas without melting (i.e., without creating liquid), a process called sublimation. Frozen carbon dioxide ("dry ice") behaves like this at room temperature on Earth--on Mars, water also behaves this way because the present atmosphere so thin. Some of the textures created by the sublimation of the polar cap include surprising circular mesas that resemble giant medicinal pills (see center right of the MOC image!).
The MOC picture is a subframe of image #7709, centered approximately at 86.86°S latitude, 76.27°W longitude. It was taken on December 29, 1997, at 3:22 PM PST, on Mars Global Surveyor's 77th orbit around Mars. The Mariner 9 image (DAS #7900063) was taken in 1972 and was the best-resolution image previously acquired. The Viking images date to 1977. The MOC subframe of #7709 was featured as Figure 6a in Malin et al., "Early Views of the Martian Surface from the Mars Orbiter Camera of Mars Global Surveyor," Science, v. 279, no. 5357, pp. 1681-1685.
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.
To MSSS Home Page