Fans in Fans
NASA/JPL/University of Arizona

Fans in Fans
ESP_020953_0925  Science Theme: Seasonal Processes
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This is a sequence of four images acquired in early southern spring over a particular spot in the South polar region. The changes in patterns are so great over just half a season that it is difficult to believe that the images cover the same ground. The subimage helps by focusing on three distinctive fans as they evolve. The dark fans turn into broad bright fans, then new small dark fans form inside the old bright fans. The newer dark fans form along cracks forming polygonal or other patterns.

These changes are driven by sublimation and condensation of volatiles, primarily carbon dioxide. Sunlight passes through the ice to warm subsurface pockets of gas, which escape to form cold jets, and the wind blows to form fans on the surface, depositing dark dust and bright frost. The cutout is from the browse images, reduced in scale about 10x, so these show only approximately one percent of the pixels in the full-resolution images.

Note: The Martian year is measured by 360 degrees of areocentric longitude of the sun or "Ls", where Ls 180-270 marks southern spring and northern fall. The Ls of each image is marked in the subimage and covers only 30 percent of the spring season.

Written by: Alfred McEwen   (16 February 2011)

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Acquisition date:15 January 2011 Local Mars time: 9:30 PM
Latitude (centered):-87.303° Longitude (East):168.356°
Range to target site:247.2 km (154.5 miles)Original image scale range:24.7 cm/pixel (with 1 x 1 binning) so objects ~74 cm across are resolved
Map projected scale:25 cm/pixelMap projection:Polarstereographic
Emission angle:0.4° Phase angle:77.4°
Solar incidence angle:77°, with the Sun about 13° above the horizon Solar longitude:217.5°, Northern Autumn
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North azimuth:235° Sub-solar azimuth:34.7°
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North azimuth:78.35°Sub solar azimuth:295.2°

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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.