Astronomy Picture of the Day

Explanation: Is it an Escher, or Mars? Three different types of surfaces visible in the North Polar Cap of Mars morph into each other in a way perhaps reminiscent of the works of M. C. Escher. On the far left dark sand covers the ground, while the centre shows a transition to a dune field. On the far right a transition is made to a much lighter surface, likely containing a larger amount of ice. Shadows indicate that lighter material holds the higher ground, with some steep cliffs on the divide. Dune shapes indicate that wind typically blows toward the upper left. Mars Global Surveyor, one of two robot spacecraft currently orbiting Mars, took the above image in early 2001. Recent images from the other orbiter, Mars Odyssey, have bolstered the hypothesis that a significant amount of water-ice lies beneath the surface near the Martian South Pole.