Curiosity is a car-sized rover designed to explore Gale Crater on Mars as part of NASA's Mars Science Laboratory mission (MSL). Curiosity was launched from Cape Canaveral on November 26, 2011, at 15:02��UTC aboard the MSL spacecraft and landed on Aeolis Palus in Gale Crater on Mars on August 6, 2012, 05:17��UTC. The Bradbury Landing site was less than 2.4��km (1.5��mi) from the center of the rover's touchdown target after a 560��million��km (350��million��mi) journey. The rover's goals include an investigation of the Martian climate and geology; assessment of whether the selected field site inside Gale Crater has ever offered environmental conditions favorable for microbial life, including investigation of the role of water; and planetary habitability studies in preparation for human exploration.
In December 2012, Curiosity's two-year mission was extended indefinitely. On August 5, 2017, NASA celebrated the fifth anniversary of the Curiosity rover landing and related exploratory accomplishments on the planet Mars.
Curiosity's design will serve as the basis for the planned Mars 2020 rover. As of December 2, 2017, Curiosity has been on Mars for 1893 sols (1944 total days) since landing on August 6, 2012. (See current status.)
The rover has a 2.1��m (6.9��ft) long robotic arm with a cross-shaped turret holding five devices that can spin through a 350�� turning range. The arm makes use of three joints to extend it forward and to stow it again while driving. It has a mass of 30��kg (66��lb) and its diameter, including the tools mounted on it, is about 60��cm (24��in). It was designed, built, and tested by MDA US Systems, building upon their prior robotic arm work on the Mars Surveyor 2001 Lander, the Phoenix lander, and the two Mars Exploration Rovers, Spirit and Opportunity.
Two of the five devices are in-situ or contact instruments known as the X-ray spectrometer (APXS), and the Mars Hand Lens Imager (MAHLI camera). The remaining three are associated with sample acquisition and sample preparation functions: a percussion drill; a brush; and mechanisms for scooping, sieving, and portioning samples of powdered rock and soil. The diameter of the hole in a rock after drilling is 1.6��cm (0.63��in) and up to 5��cm (2.0��in) deep. The drill carries two spare bits. The rover's arm and turret system can place the APXS and MAHLI on their respective targets, and also obtain powdered sample from rock interiors, and deliver them to the SAM and CheMin analyzers inside the rover.
Since early 2015 the percussive mechanism in the drill that helps chisel into rock has had an intermittent electrical short. In December 2016 the drill feed motor caused a malfunction that prevented the rover from moving its robotic arm and driving to another location. Internal debris is suspected of causing the fault.
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Rover role in the landing system
Previous NASA Mars rovers became active only after the successful entry, descent and landing on the Martian surface. Curiosity, on the other hand, was active when it touched down on the surface of Mars, employing the rover suspension system for the final set-down.
Curiosity transformed from its stowed flight configuration to a landing configuration while the MSL spacecraft simultaneously lowered it beneath the spacecraft descent stage with a 20��m (66��ft) tether from the "sky crane" system to a soft landing���wheels down���on the surface of Mars. After the rover touched down it waited 2 seconds to confirm that it was on solid ground then fired several pyros (small explosive devices) activating cable cutters on the bridle to free itself from the spacecraft descent stage. The descent stage then flew away to a crash landing, and the rover prepared itself to begin the science portion of the mission.