Polygons, polygons, as far as the eye can see. That was the surreal view that greeted the Mars Phoenix Lander when it touched down on the Red Planet鈥檚 enigmatic northern plains on 25 May.
Phoenix landed well inside the planet鈥檚 arctic circle, in a region where permanent ground ice is believed to lie very near the surface. Such ice may have made the polygon pattern pictured.
In polar regions on Earth, these polygons form with the seasonal expansion and contraction of ground ice. When the ice becomes very cold it contracts and fractures in geometric patterns, like cracks in desert mud. If they fill in with material, such as dry Martian dust, the ground ice will have no room to expand again when the temperature rises. The ground ice buckles as a result, producing low mounds.
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The polygons suggest that ice is within 30 centimetres of the surface 鈥� well within reach of the lander鈥檚 digging arm. Phoenix will scrape away at the top soil until it reaches the ice, which it will test for the presence of organic molecules that may once have fostered life. It will also look for clues that the ice melted during periods when the polar regions of Mars were more directly oriented towards the sun 鈥� such water may have periodically created habitable conditions.
鈥淭his is a scientist鈥檚 dream,鈥� says Peter Smith, principal investigator for the mission, planned to last for 90 Martian days, or sols. However, it could last until January, when the Martian winter sets in. By April 2009, Phoenix will have perished under metres of frozen CO2.
Mars 鈥� Mars is full of surprises, learn more in our continually updated .
