The Curiosity Rover continues its journey across the surface of Mars and is sending back they made the images of the surface of the red planet. On the NASA website posted one of these pictures was taken on 7 August 2016 right by a camera mounted on the Rover.
In this picture is clearly visible an object similar to a stone, but which is moving along the surface of the big stone has left its clear mark (scratch). What explains this anomaly, NASA will not comment on.
This image was taken by Mastcam: Right (MAST_RIGHT) onboard NASA’s Mars rover Curiosity on Sol 1423 (2016-08-07 06:32:01 UTC).