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.
The 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. This leads researchers to believe that the Mars region was covered in water or water ice when it was hit about 2.3 million years ago.