Mars Pathfinder carried Sojourner, the first successful rover to operate on Mars, during NASA’s 1997 mission.
The Pathfinder lander reached Mars on 4 July 1997 using an innovative airbag-assisted landing system. After deployment, the small Sojourner rover drove onto the surface and examined rocks and soil in the Ares Vallis region.
Sojourner was only about the size of a microwave oven, but it demonstrated autonomous navigation, robotic mobility, and remote geological investigation. It communicated primarily through the lander, which relayed data to Earth. The mission vastly exceeded its planned design life of one week for the lander and seven days for the rover.
Mars Pathfinder is the spacecraft mission name, while Sojourner is the rover’s name. Viking 1 and Viking 2 had landed earlier, in 1976, but they were stationary landers rather than rovers.