The Pathfinder plunged into the Martian atmosphere, deployed a parachute and inflated a set of high-tech air bags, surrounding itself with the equivalent of a beach ball 15 feet in diameter. For a detailed diagram of the landing, go here.
The "beach ball," which entered the Martian atmosphere at 17,000 mph, hit the rock-strewn surface of Mars at about 55 mph and bounced once, twice, maybe 10 times before coming to rest. The air bags deflated. The petals of the lander unfolded, releasing a tiny robot -- the Rover -- that scooted down a ramp and headed out to explore its surroundings, analyze rocks and take pictures.
Engineers tested Pathfinder's air bag system in the Summer of 1995. The air bags, composed of four large bags with six smaller, interconnected spheres within each bag, deployed about 330 feet above the Martian surface, and allowed Pathfinder to land on rougher terrain than previous probes.
Doug Petercsak, a UT graduate, designed the motors that operated the Pathfinder's cameras and air bags. See his story here.