There are many thin crusty structures on Mars. Curiosity's mast camera took this pic, including different types of rock with a planar form. Apparently these are often formed by consolidation of sedimentary material, and later excavated by a thin sandblasting wind. But the range of physical processes that formed them are not clear.
[original image: 0317ML1300021000E1_DXXX.jpg, contrast stretched to highlight structure and color differences.]
