A landing system built around impact
Pathfinder had to arrive intact on a planet with a thin atmosphere and an uneven surface. A parachute could slow the spacecraft, but not enough to make a gentle touchdown by itself. Landing legs would have added weight and still had to cope with rocks and slopes the team could not reliably avoid.
The solution was to protect the lander itself. Shortly before touchdown, airbags inflated around it, forming a padded shell. The spacecraft then struck the ground inside that shell rather than relying on a set of legs to absorb the force at a few points.
Why bouncing was part of the plan
The airbags were designed to deform and rebound, spreading the shock of impact and letting the lander tumble or bounce across the surface without being crushed. The goal was not to control each bounce, but to keep the spacecraft protected until the uneven terrain finally brought it to rest.
That approach shifted the engineering problem: instead of needing a perfectly chosen, level landing spot, Pathfinder needed a cushion tough enough to handle an uncertain sequence of impacts. Once the bouncing stopped, the airbags could be deflated and the lander could open its panels. The rover Sojourner, carried inside, could then roll out to explore.
The memorable part of the landing was also its practical payoff: Pathfinder could reach the Martian ground without landing legs, even when the ground was too rough to promise a clean, upright touchdown.
