Mars 360                             Views of the Red Planet 1 2 3 4 5 6 7 8 9 10 11 12 'Festoon' Pattern Opportunity imaged distinctive, smile-shaped features called "festoons," seen on the surface of this rock. The detailed geometric patterns -- nested sets of concave-upward layers -- in sedimentary rocks imply the presence of small, sinuous sand ripples that form only in water on Earth. Essentially, the festoons are the preserved remnants of tiny (centimeter-sized) underwater sand dunes formed long ago by waves in shallow water on the surface of Mars. + Full image and caption     Jet Propulsion Laboratory    California Institute of Technology