Help NASA Classify Martian Craters . ... Credit Copyright: Sonie Lau , NASA Ames Explanation: The large Martian crater above just left of center: is this a fresh crater, a degraded crater, or a ghost crater? ... Additionally, there are so many craters on Mars that NASA just doesn't have enough people to classify them all! ... Degraded craters are typically older and have their rims more rounded, while "ghost craters" are the oldest of all and only faintly discernable. ... NASA Official: Jay Norris. ...