Close-up view of the HiRISE image of Holden crater (right) shows layers revealed when the rim was breached, unleashing water that scoured parts of the crater. From the bottom up, these include the base of impact megabreccia, contrasting smooth sedimentary layers, another darker, crudely layered unit, and dark wind-blown material on the surface. These layers correspond to layers in the drawing (left). NASA/JPL/University of Arizona/J. Grant et al
