Layered Hills in Arabia Terra on Mars . ... Credit Copyright: MSSS , JPL , NASA Explanation: Why are some hills on Mars so layered? ... Clearly, dark windblown sand surrounds outcropping of light sedimentary rock across the floor of crater Arabia Terra . ... Blown sand possibly itself eroded once-larger mesas into the layered hills . ... The above image , showing an area about 3 kilometers across, was taken in 2003 October by the now defunct Mars Global Surveyor spacecraft orbiting Mars . ...