The wheels and suspension system have been installed on NASA's next Mars rover, Curiosity, a key step in assembly and testing of the flight system for the Mars Science Laboratory mission slated to launch next year. The centerpiece of MSL, Curiosity has six wheels and a rocker-bogie suspension system like its smaller predecessors: Spirit, Opportunity and Sojourner. Each wheel has its own drive motor and the corner wheels also have independent steering motors. Unlike earlier Mars rovers, Curiosity will also use its mobility system as landing gear when the mission's rocket-powered descent stage lowers the rover directly onto the Martian surface on a tether in August 2012.