March 11, 2014
This is the explanation of NASA :
Mars’ northern-most sand dunes are beginning to emerge from their winter
cover of seasonal carbon dioxide (dry) ice. Dark, bare south-facing slopes are soaking up the warmth of the sun.
At first glance this hilly desert landscape appears to show islands of trees casting shadows on reddened soil.But the trees are actually dark material to streak down the slopes.
The steep lee sides of the dunes are also ice-free along the crest, allowing sand to slide down the dune. Dark splotches are places where ice cracked earlier in spring, releasing sand. Soon the dunes will be completely bare and all signs of spring activity will be gone.
But Author Arthur C. Clarke has a different opinion and noted that these forms appear to change with the seasons, growing with the warmth and increased sunlight of Mars’s spring season, just as vegetation would. The photo above, reveals much larger forms that look like spreading trees as seen from above.
Scientists believe water activity affected the plateau after the formation of the nearby canyons. Although the source of water and sediment remains uncertain.
The image was acquired by the HiRISE camera aboard NASA’s Mars Reconnaissance Orbiter on Jan. 16, 2014.
The Mars Reconnaissance Orbiter Project is managed by NASA’s Jet Propulsion Laboratory, Pasadena, Calif., for NASA’s Science Mission Directorate, Washington. JPL is a division of the California Institute of Technology in Pasadena.
HiRISE is operated by the University of Arizona, Tucson. The instrument was built by Ball Aerospace & Technologies Corp., Boulder, Colo. Malin Space Science Systems, San Diego, built and operates the Context Camera.
Thanks to: http://missiongalacticfreedom.wordpress.com