Depending on how old the surface is, it can be seen that the number of craters on Mars varies from place to place on the surface.
Most of the surface of the Southern Hemisphere is very old, and there are many craters. This is where Hellas Planitia, the planet’s largest crater at 1,400 miles (2,300 km), is found.
As the Northern Hemisphere ages, so do the craters. There are only a few craters in the volcano, so this suggests that they may have erupted recently, and we can assume that the resulting lava covered any old craters.
Some craters are surrounded by solid mudflow-like debris, which is thought to have been caused by the impact of the crater on groundwater or ice.