The Deceleration Subsystems are used to reduce Pathfinder's velocity and allow a safe landing on Mars. These subsystems consist of an aeroshell, or heat shield to protect the spacecraft as it comes into the atmosphere, a parachute to slow the descent, small solid rockets to further slow the descent, a radar altimeter to indicate proximity of the surface, and airbags which inflate to protect against impact. The parachute and aeroshell are derived from technology used successfully in the Viking landings. The airbags are a new feature which are basically designed like the airbags which protect motorists during automobile crashes.
The lander is shaped like a tetrahedron. The tetrahedron consists of four similarly-shaped triangular panels. All lander equipment except the solar arrays and rover are attached to a single center panel. The other three panels are attached to the edges of the center panel. These three panels can move in a way that would flip the lander into an upright position if it should land upside-down. The lander is designed to last a minimum of 30 days on the Martian surface.
The microrover has 6 wheels and a mass of about 10 kg. It is about 65 cm long by 45 cm wide and 32 cm high. The rover will allow scientists to examine rocks that would otherwise be out of reach from a fixed lander. The rover will also be able to look at the lander and check out its condition. The microrover carries the Alpha Proton X-ray Spectrometer (APXS) experiment. It also has two small cameras which act as "eyes" for navigating the rover around the landscape. These imagers can see objects about one millimeter in size and may allow scientists a close-up view of the texture of rocks found at the landing site. The rover is expected to function for a minimum of 7 days, but hopefully will last 30 or more days on the martian surface.