Humans have not been to Mars, but several unmanned spacecraft have been sent there. The first spacecraft to land on Mars was the Viking lander in 1976. Since then, several other landers and rovers have been sent to Mars, including the Mars Pathfinder lander in 1997 and the Mars Exploration Rovers Spirit and Opportunity in 2004. The Curiosity rover landed on Mars in 2012, and is still exploring the planet.