The appearance of an impact crater depends on several factors, including the material in which the crater was formed and the size of the impact itself. This image covers a rocky peak in the center of an unnamed crater, approximately 40 kilometers across.
When crater diameters on Mars exceed 5 to 8 kilometers, their shape changes from a simple, bowl-like depression to a more complex form. Rocks under the center of the crater rise as they rebound from the impact shock, lifting materials from below the surface to a peak in the center of the crater. This uplift of rocks from depth provides scientists a window into the composition of the subsurface, making crater central uplifts interesting targets for HiRISE images. [More at link]