Why do all the rocks on Mars lie on top of the soil? One would think that after all those billions of years they would be mostly covered over with dirt, like on the moon.
The difference is Mars has atmosphere and more recently had volcanic activity.
Many rocks are covered but martian storms often blow the soil away. Leaving only large rocks on top in certain areas. While other areas are covered in very deep dunes. The sand/soil is constantly shifting due to winds.
The moon has no atmosphere so the surface is constantly bombarded and doesnt move much otherwise. With each bombardment, rock is broken down and the lunar soil becomes finer.