This image looks remarkably like groves of trees growing among Martian dunes. But, the trees are an optical illusion. They are actually dark streaks of sediment on the downwind side of the dunes. They were created by escaping gas from the evaporating carbon dioxide ice below. The bottom of the ice melts into vapor and moves toward holes in the ice, carrying dark sediment along with it that is then deposited when the gas escapes.

This false-color image looks like it could be of the desert southwest in North America. These gully channels running from a cliff area near the crater rim show typical shapes made by water-carved streams on Earth. The image was taken by the High Resolution Imaging Science Experiment (HiRISE) camera on the Mars Reconnaissance Orbiter.