Wind, Water, and Lava

The three main geological agents acting on the Martian surface are visible in this image, within an outflow channel to the east of the Tharsis volcanos and north of Valles Marineris. In a wide channel previously eroded by water, linear features have been eroded into the rock by the wind. Some of the material that may have eroded the surface are trapped within the crater, forming mega-ripples (a dune form). Later, lava flows embayed the streamlined rocks. A second, younger flow lobe is visible at the bottom of the image.