 Self-secondary craters are a those that form from ejected material of a primary crater but that are ejected at such an angle that the ejected material makes an impact within the primary crater itself.Self-secondary craters have caused much controversy with scientists who excavate cratered surfaces with the intent to identify its age based on the composition and melt material.An observed feature on Tycho has been interpreted to be a self-secondary crater morphology known as palimpsests.