The rover's energy
The rover requires power to operate. Without power, it cannot move, use its science instruments, or communicate with Earth. The Mars Science Laboratory rover carries a radioisotope power system that generates electricity from the heat of plutonium's radioactive decay. This power source gives the mission an operating lifespan on Mars' surface of at least a full Martian year (687 Earth days) or more while also providing significantly greater mobility and operational flexibility, enhanced science payload capability, and exploration of a much larger range of latitudes and altitudes than was possible on previous missions to Mars.