A Mars rover is a spacecraft which propels itself across the surface of Mars after landing.

Rovers have several advantages over stationary landers: they examine more territory, they can be directed to interesting features, they can place themselves in sunny positions to weather winter months and they can advance the knowledge of how to perform very remote robotic vehicle control.

Their advantages over orbiting spacecraft are that they can make observations to a microscopic level and can conduct physical experimentation. Disadvantages of rovers compared to orbiters are the higher chance of failure, due to landing and other risks, and that they are limited to a small area around a landing site which itself is only approximately anticipated.

There have been three successful Mars rovers, all of which were robotically operated. (There have also been two successful non-Martian robotic rovers: in the 1970s the USSR sent two Lunokhod rovers to the Moon.)

For more information about Mars rover, read the full article at Wikipedia.
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