This composite image was taking by MAHLI (Mars Hand Lens Imager).
MAHLI took an image with its reclosable dust cover open for the first time on Mars, confirming sharp imaging capability that had been obscured by a thin film of dust on the cover during previous use of the camera. It took images of cameras at the top of Curiosity's mast, of the underbelly of the rover and of MAHLI's own calibration target, among other pointings.