HiRISE | Seasonal Erosion (ESP_029545

NASA/JPL/University of Arizona

Seasonal Erosion
ESP_029545_0950 Science Theme: Seasonal Processes

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Bright carbon dioxide frost (or, dry ice) highlights this network of channels carved into the surface. The channels are eroded a little bit every spring when the seasonal polar cap, composed of dry ice, sublimates (meaning going directly from a solid to gas) at the ice-surface interface. The erosion occurs under the seasonal ice layer: when trapped pressurized gas finds an escape route it carries along loose surface material. This surface material is blown downwind and deposited in dark fans on top of the seasonal ice layer.

The trapped gas finds the weakest easiest escape route. In this area the gas exploited the existing polygonal structure of the surface below. Polygonal terrain is common at high latitudes, and is caused by the thermal contraction and expansion of water ice frozen in the surface dirt.

Written by: Candy Hansen (audio by Tre Gibbs) (16 January 2013)

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Acquisition date:	14 November 2012	Local Mars time:	5:27 PM
Latitude (centered):	-85.039 degrees	Longitude (East):	259.056 degrees
Range to target site:	248.8 km (155.5 miles)	Original image scale range:	49.8 cm/pixel (with 2 x 2 binning) so objects ~149 cm across are resolved
Map projected scale:	50 cm/pixel	Map projection:	POLAR STEREOGRAPHIC
Emission angle:	5.5 degrees	Phase angle:	82.8 degrees
Solar incidence angle:	78 degrees, with the Sun about 12 degrees above the horizon	Solar longitude:	206.9 degrees, Northern Autumn
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North azimuth:	118 degrees	Sub-solar azimuth:	34.7 degrees
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North azimuth:	169.0 degrees	Sub solar azimuth:	86.28 degrees

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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.