Sojourner was the first robot to appear on a U.S. postage stamp, issued in 1997.
NASA’s Sojourner rover was part of the Mars Pathfinder mission, which landed on Mars on July 4, 1997. The small six-wheeled vehicle was named after Sojourner Truth, the 19th-century American abolitionist and women’s-rights activist. It examined rocks and soil near the landing site while communicating through the Pathfinder lander.
The U.S. Postal Service issued a Mars Pathfinder stamp in 1997 featuring the mission and its rover. The stamp helped make the robotic exploration of Mars familiar to a broad public audience. Sojourner itself operated for about 83 sols, or Martian days, despite being designed for a much shorter mission.
Spirit and Opportunity were later Mars rovers, landing in 2004, while Curiosity arrived in 2012. They are sometimes recalled first because they operated for much longer and carried larger scientific instruments. Sojourner’s significance is its earlier role as the first mobile rover successfully operated on Mars and its place on the 1997 stamp.