Wheels and legs
The Mars Exploration Rover has six wheels, each with its own individual motor.
The two front and two rear wheels also have individual steering motors (1 each). This steering capability allows the vehicle to turn in place, a full 360 degrees. The 4-wheel steering also allows the rover to swerve and curve, making arching turns.
The rover is designed to withstand a tilt of 45 degrees in any direction without overturning. The rover's design allows the rover to go over obstacles or through holes that are more than a wheel diameter (25 centimeters) in size.
The rover has a top speed on flat hard ground of 5 centimeters (2 inches) per second. However, in order to ensure a safe drive, the rover is equipped with hazard avoidance software that causes the rover to stop and reassess its location every few seconds. So, over time, the vehicle achieves an average speed of 1 centimeter per second. The rover is programmed to drive for roughly 10 seconds, then stop to observe and understand the terrain it has driven into for 20 seconds, before moving safely onward for another 10 seconds.