The first Mars roving vehicle, landed by NASA on the planet on 4 July 1997 by its Mars Pathfinder space probe. The rover, about the size of a microwave oven, weighed 11 kg. NASA specialists controlled Sojourner from Earth, sending it down a ramp from the Pathfinder and over a Martian plain to take photographs and measure and analyse rocks for nearly three months. But the rover outlasted its life expectancy by 12 times. Sojourner sent back to Earth more than 550 images, as well as more than 15 chemical analyses of rocks and soil and extensive data on winds and other weather factors.

Having landed on the US Independence Day, it was named after Sojourner Truth, a former slave who had campaigned for abolitionism and equal rights for women.