Using images from Dawn NASA has produced this fascinating animation of Ceres: What struck me while watching is the fact that most craters look almost perfectly round in shape. Perhaps it is the same for other bodies, I just never thought about it earlier. Intuitively I would expect the crater shape to depend on the hit angle, and hit angles to be mostly random. Sure, few craters are oval, but the majority looks like a result of a hit perpendicular to the surface. Obviously gravity can skew the distribution of hit angles, but somehow I doubt it would eliminate tangential hits. What am I missing?