Which NASA mission deployed the first rover to operate on Mars, landing in July 1997?

Mars Pathfinder deployed the first rover to operate on Mars when it landed on July 4, 1997.

The mission delivered the small Sojourner rover to Ares Vallis using an innovative landing system of airbags. After the lander reached the surface, Sojourner drove down ramps and examined rocks and soil with its instruments.

Sojourner was a technology demonstration as well as a science mission. It tested autonomous navigation and rover operations on another planet while the Pathfinder lander photographed the surrounding terrain and analyzed atmospheric conditions.

Pathfinder is sometimes confused with Viking 1, which achieved the first successful U.S. soft landing on Mars in 1976 but did not carry a rover. Later NASA rovers, including Spirit, Opportunity, Curiosity, and Perseverance, were much larger.