When did the first robot rover go to Mars?

The first robot rover to land and travel on Mars was the Mars Pathfinder's Sojourner Rover. It rolled onto Mars' surface on July 6, 1997. The Sojourner Rover was a six-wheeled vehicle that was controlled remotely by an operator here on Earth. Because of the distance to Mars, commands sent to the rover from Earth took about 10 minutes to reach it. Also, information sent back by the rover took another 10 minutes to reach Earth. The rover's mission was to gather information about the soil and rocks of Mars. Information on Sojourner Rover's performance on Mars was used to help design better robot rovers for subsequent missions.