The arm and the remote sensing mast of the Mars rover Curiosity each carry science instruments and other tools for NASA's Mars Science Laboratory mission. This image, taken April 4, 2011, inside the Spacecraft Assembly Facility at NASA's Jet Propulsion Laboratory, Pasadena, Calif., shows the arm on the left and the mast just right of center. For scale, the white segment of the arm extending vertically from its connection to the rover body is about 0.6 meter (2 feet) long.

A percussive drill and sample-handling system on the arm will prepare samples of fine powder taken from interiors of Martian rocks and deliver them to two analytical instruments inside the rover. The turret of tools at the end of the arm -- in the far left in this image -- also has a color camera, an element-identifying spectrometer, a scoop for collecting soil samples and a brush for cleaning rock surfaces.

The circle in the white box at the top of the mast is the laser and telescope of an instrument that can zap a rock up to about 7 meters (23 feet) away and determine its composition from a spark generated by the laser. Just below that circle is the square opening for a wide-angle camera that is paired with a telephoto camera (the smaller square opening to the left) in the rover's primary scientific camera, which can take high-definition color video with both "eyes." Two stereo navigation cameras on the mast will provide three-dimensional information about the rovers surroundings for use in driving and planning other rover operations. Partway up the mast are sensors for the mission's weather station.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Science Laboratory Project for the NASA Science Mission Directorate, Washington.