Sojourner was the small rover carried to Mars by NASA’s 1997 Pathfinder mission.
Mars Pathfinder landed in Ares Vallis on July 4, 1997. Its rover, named Sojourner after American civil rights leader Sojourner Truth, became the first wheeled vehicle to operate on another planet. The rover weighed about 10.5 kilograms and communicated through the Pathfinder lander, which also served as a stationary science platform.
Sojourner used six wheels and carried an Alpha Proton X-ray Spectrometer to examine the composition of rocks and soil. It investigated nearby rocks nicknamed Barnacle Bill and Yogi, helping scientists compare their chemistry. The rover was designed for a seven-sol mission but operated for about 83 sols.
The mission demonstrated an inexpensive landing approach using airbags and showed that a mobile robot could explore terrain around a lander. Later NASA rovers—Spirit, Opportunity, Curiosity, and Perseverance—were much larger and more capable, but Sojourner established the basic idea of driving across Mars to choose targets beyond the landing site.