Curiosity took the four images for this mosaic with the MAHLI microscopic imager on sol 400 (September 21, 2013). The image contains a ridge that stands higher than surrounding rock. The ridge resulted from a crack or vein in the surrounding rock becoming filled with material that was subsequently more resistant to erosion than the material of the surrounding rock. Researchers are investigating the textures and composition of ridges and the surrounding rock, which is a pebbly sandstone conglomerate. Reddish dust coats the surfaces seen in this image. The underlying rocks are gray, varying from nearly white to nearly black. The host rock in which the crack or vein formed is obscured in this image by the coating of dust and a thin layer of the rock's own debris -- loose pebbles and sand.

NASA / JPL / MSSS