The left eye of the Mast Camera on NASA's Mars rover Curiosity took this image of the camera on the rover's arm, the Mars Hand Lens Imager (MAHLI), on Sept. 5. MAHLI is one of the tools on a turret at the end of the rover's robotic arm.
The image shows that MAHLI has a thin film or coating of Martian dust on it. This dust accumulated during Curiosity's final descent to the Martian surface, as the Mars Science Laboratory spacecraft's descent stage (or sky crane) engines were disrupting the surface nearby. The mechanism at the right in this image is Curiosity's
dust removal tool, a motorized wire brush.