So, the circle is WAY too small to be a RAT mark, however, I believe it is the IMPRESSION of a PHILLIPS HEAD SCREW, pressed into the soil when the robot was trying to move the arm end in close.
Take a look, and imagine what you would get if you pressed a flat, phillips head screw into the soil. Also imagine that it screwed into an enclosure, so a "ring" could form in the space between the screw head and the enclosure surface.
That is my reasoned opinion. It is an artifact produced by the rover itself, and if the cause is correct, we should be able to find "others" wherever the camera was pushed into a softer surface.