The Curiosity rover took its first scoop of Martian soil this past summer. This achievement, like nearly everything the rover has done since its dramatic landing on Mars, was made possible by 31 actuators. Each actuator consists of an encoder, a brushless DC motor, a planetary gearbox, a brake, and a resolver.
The actuators, made by Aeroflex Corp., are located throughout the rover, and are responsible for most of its moving parts, including its wheels, robotic arm, and remote sensing mast (the rover's "head"), among others.
Today, these actuators are driving Curiosity around on the surface of Mars. But engineering difficulties with the actuators caused the mission's launch to be delayed by two years (the first such launch-date slip since the Viking program in the 1970s), and put the program at risk of cancellation by Congress.