HiRISE at One Year: Student Image of the Week-Seasonal Changes of South Polar Dark Dune Field
NASA/JPL/University of Arizona

HiRISE at One Year: Student Image of the Week-Seasonal Changes of South Polar Dark Dune Field
PSP_003609_1110  Science Theme: Fluvial Processes



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This image was suggested by Andras Sik's SUPERNOVA astronomy and space research class at the Alternative Secondary School of Economics in Budapest, Hungary.

They interpret the image: "During local springtime, a varying albedo pattern can be observed on the surface of dark intracrater dune fields in the southern polar region of Mars. The origin of dark dune spots and the dark slope streaks emanating from them is yet uncertain. There are several possible explanations for these phenomena, like "sublimation of carbon-dioxide frost cover", "dusty carbon-dioxide gas eruptions through the frost cover" and "transient liquid water-formation under layered water-ice/carbon dioxide-ice cover". In this HiRISE image the distribution of dark streaks are not chaotic and their shapes are not fan-like; rather they are composed of confined, dozen-hundred meter long branches which follow the local topography and have accumulation zones at their end."

We are learning a great deal from the enigmatic dark spots that are found throughout the south polar region. These dark spots may have resulted from cold gas jets that form by sublimation of the ice bringing entrained dust to the surface. Small dark streaks may have formed by avalanches of sand or they may be patches of coarse-grained ice that are clear enough so that the dark material below the ice is visible.

The color image also provides helpful clues to understand this process. Bright white frost can be seen covering the surface. This frost is a probably a combination of frozen water and carbon dioxide ice. These bright patches are particularly prevalent along dune slip faces and around dark spots.Written by: Alix Davatzes (HiRISE challenge caption)   (18 November 2007)

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Acquisition date:04 May 2007 Local Mars time: 3:52 PM
Latitude (centered):-68.868° Longitude (East):209.496°
Range to target site:250.1 km (156.3 miles)Original image scale range:25.0 cm/pixel (with 1 x 1 binning) so objects ~75 cm across are resolved
Map projected scale:25 cm/pixelMap projection:Polarstereographic
Emission angle:3.2° Phase angle:63.5°
Solar incidence angle:61°, with the Sun about 29° above the horizon Solar longitude:231.5°, Northern Autumn
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North azimuth:98° Sub-solar azimuth:31.0°
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North azimuth:119.4°Sub solar azimuth:52.83°

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For information about NASA and agency programs on the Web, visit: http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.