HiRISE: Ejecta in excess

When impact craters are formed, the material that once resided in the subsurface is blown upward and outward. This material falls back and settles around the newly formed crater into what is called an “ejecta blanket.” It often appears as a layer on top of the original surface extending radially outward from the crater. In some cases the volume of the ejecta material — mainly rocky debris — appears to exceed the volume of the original crater, presenting something of a puzzle. One hypothesis is that the original surface…. [More at link]