Like the Spirit and Opportunity rovers, Curiosity will have a "rocker-bogie" suspension system, which keeps it from tipping over when rolling over large rocks or hitting dips in the Martian terrain. But unlike the earlier rovers, Curiosity will use its wheels as landing gear when a rocket-powered descent lowers it directly onto the Martian surface via a tether in August 2012. When Spirit and Opportunity touched down on Mars in January 2004, they were cushioned from the bumpy landing by the airbags that held them. But despite the protection, airbag landings introduce additional risks during the egress phase -- the period of time between the actual landing and driving the rover off the lander onto the Martian surface. Egress involves a series of tactical moves and steps, so the flight team must give the rover commands and assess the resulting data before proceeding with the next step.