Bits of sand are picked up and carried off by the wind, which can then blast the sides of nearby rocks, buffing and polishing them smooth. On the seashore, the action of waves chips away at cliffs ...

NASA's Mars rover has pictured a mysterious, skull-shaped rock on the Red Planet ... formed via the erosion of clasts from the rock or scouring by wind," NASA said. "Alternatively, 'Skull Hill ...

This time, it has to do with a skull-shaped rock rather than ... formed from erosion — either by wind or through the removal of clasts, which are small rock fragments. Another possibility ...