Mysterious Pits in Mars Crater

This fascinating observation shows us a dark-toned mound with pits inside an impact crater (http://static.uahirise.org/images/201...). Are these pits the result of sublimation? The crater itself is an ancient one, as evidenced by the eroded rim. For the mound inside, HiRISE resolution can give us a closer look at textural features that might help explain what we're looking at: layers in pit walls, or perhaps cracks from expansion?