Violent impact on Mars left billions of craters - and an important clue. Scientists believe that asteroids large enough to create a crater of this size only hit Mars every three million years.
Mars' Corinto crater is the youngest large crater on the red planet. Impact on Mars created about two billion craters, of which the study mentions about 2 billion, lie mainly south and southwest of Corinto. The craters near the main crater are shaped like semicircles, while the craters further away are more elongated and flat.