Mars rovers are automated, motorized vehicles that travel across the surface of Mars. They are much more useful than landers, which do not travel around. Rovers can explore more ground, be directed to interesting features, and place themselves in sunny positions to survive the winter months.
There have been four successful Mars rovers:
Sojourner, from the NASA Mars Pathfinder mission, landed on Mars in 1997. It explored the Martian surface for 3 months, using solar power during the day and a large battery during the night. Sojourner had cameras facing forwards and backwards, and many other scientific instruments.
Spirit and Opportunity were both part NASA's Mars Exploration Rover mission. They launched in 2003, and landed on opposite sides of Mars. In 2009, Spirit became stuck in soft soil on the Martian surface. The rover continued to take scientific data until 2010. Opportunity is still active and gathering data, 13 years after the end of the planned mission! The rover studies meteorites and craters, and the Martian soil.
Curiosity is part of the NASA Mars Science Laboratory. It landed on Mars in 2012, and its science goals are:
- to investigate the climate of Mars
- to investigate Martian rocks and soils
- to look for evidence of past or present water
- to consider how suitable Mars is to human life