The Rock Abrasion Tool (RAT) is a grinder and brush installed on the MER-A (Spirit) and MER-B (Opportunity) Mars rovers that brushes and grinds rock surfaces.

The RAT weighs 0.7 kilograms (1.5 pounds) and draws 30 watts of power, less than most light bulbs. It is approximately the size of a soda can. It is installed on the turret, or "hand," of the rovers' arm. It can abrade approximately a quarter centimeter of rock per hour from a hard rock surface. Once the underlying rock is exposed, the MERs' imagers and spectrometers analyse the rock.