HiRISE | Spring Fans (ESP_029577

NASA/JPL/University of Arizona

Spring Fans
ESP_029577_0925 Science Theme: Seasonal Processes

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At high latitudes every winter carbon dioxide condenses from Mars' atmosphere onto the surface forming a seasonal polar cap. In the spring, the Sun shines through this semi-translucent layer of dry ice and heats the ground below.

The ice sublimates (goes directly from ice to gas) on the underside of the seasonal ice layer and the gas is trapped. When the pressure is high enough the ice cracks and ruptures allowing the gas to escape. When the conditions are optimal this gas may condense locally near the source, forming a bright fan.

The dark fans are fine bits of surface material that get carried along by the escaping gas up to above the surface ice. Fine particles are also carried downwind and deposited in dark fans on top of the ice, where they may slowly sink into the ice. The rows of dark fans outline the original crack in the ice that allowed the gas to escape.

Written by: Candy Hansen (audio by Tre Gibbs) (24 January 2013)

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Acquisition date:	17 November 2012	Local Mars time:	9:36 PM
Latitude (centered):	-87.302 degrees	Longitude (East):	168.114 degrees
Range to target site:	247.3 km (154.6 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/pixel	Map projection:	POLAR STEREOGRAPHIC
Emission angle:	0.6 degrees	Phase angle:	81.0 degrees
Solar incidence angle:	81 degrees, with the Sun about 9 degrees above the horizon	Solar longitude:	208.4 degrees, Northern Autumn
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North azimuth:	179 degrees	Sub-solar azimuth:	34.0 degrees
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North azimuth:	78.11 degrees	Sub solar azimuth:	293.7 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.