Credit: HiRISE, MRO, LPL (U. Arizona), NASA
Explanation: They might look like trees on Mars, but they're not.
Groups of dark brown streaks have been photographed by the Mars
Reconnaissance Orbiter on melting pinkish sand dunes covered with light
frost. The above image was taken in 2008 April near the North Pole of
Mars. At that time, dark sand on the interior of Martian sand dunes
became more and more visible as the spring Sun melted the lighter
carbon dioxide ice. When occurring near the top of a dune, dark sand
may cascade down the dune leaving dark surface streaks -- streaks that
might appear at first to be trees standing in front of the lighter
regions, but cast no shadows. Objects about 25 centimeters across are
resolved on this image spanning about one kilometer. Close ups of some
parts of this image show billowing plumes indicating that the sand
slides were occurring even when the image was being taken."
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