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25-Mar-2009
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HiRISE Sees Signs of an Unearthly Spring
University of Arizona Press Release
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Starburst Spider
Mars' seasonal cap of carbon dioxide ice has eroded many beautiful terrains as it sublimates (goes directly from ice to vapor) every spring. In the region where the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter took this image, we see troughs that form a starburst pattern. In other areas these radial troughs have been refered to as spiders, simply because of their shape. In this region the pattern looks more dendritic as channels branch out numerous times as they get further from the center.
The troughs are believed to be formed by gas flowing beneath the seasonal ice to openings where the gas escapes, carrying along dust from the surface below. The dust falls to the surface of the ice in fan-shaped deposits.
This image, covering an area about 1 kilometer (0.6 mile) across, is a portion of the HiRISE observation catalogued as ESP_011842_0980, taken on Feb. 4, 2009. The observation is centered at 81.8 degrees south latitude, 76.2 degrees east longitude. The image was taken at a local Mars time of 4:56 PM and the scene is illuminated from the west with a solar incidence angle of 78 degrees, thus the sun was about 12 degrees above the horizon. At a solar longitude of 203.6 degrees, the season on Mars is northern autumn.
Image Credit: NASA/JPL-Caltech/University of Arizona
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The Answer is Blowing in the Wind
Every winter Mars' polar region is covered with a layer of seasonal carbon dioxide ice (dry ice). In the spring jets of gas carry dust from the ground up through openings in the ice. The dust gets carried downwind by the prevailing wind and falls on top of the seasonal ice layer in a fan-shaped deposit. Many jets appear to be active at the same time since numerous fans are all deposited in the same direction.
This image from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter appears to show several times at which jets were active. At the top of this image the fans are oriented in one direction while at the bottom they are going in a different direction. This suggests that as the ice layer thins, a set of gas jets becomes active, they die down, then further away another set starts up at a later time with a different prevailing wind direction.
This is a reduced-resolution image from the HiRISE Observation observation catalogued as ESP_011934_0945, taken on Feb. 11, 2009. The observation is centered at 85.4 degrees south latitude, 104.0 degrees east longitude.
The image was taken at a local Mars time of 6:12 p.m.and the scene is illuminated from the west with a solar incidence angle of 79 degrees, thus the sun was about 11 degrees above the horizon. At a solar longitude of 207.9 degrees, the season on Mars is northern autumn.
Image Credit: NASA/JPL-Caltech/University of Arizona
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