Wind-sculpted Rocks

Because it does not rain on Mars, the wind is free to shape the surface to the extent that it becomes clear even in spacecraft images. This images shows parallel grooves oriented north to south, slowly eroded by winds of the same alignment. At the bottom of the image, a round mesa is most likely aninverted crater -- that is, a crater that has withstood the wind erosion to such a degree that it remains on the surrounding plains as a protruding structure, rather than a hole in the ground.