When the Curiosity rover touched down on Mars yesterday, a specially designed nuclear generator kicked into action.

Previous Mars missions have relied on solar panels to power the rovers, but exploration was slowed down by dust build-up on the solar panels or short winters days with little sunlight. The Curiosity Rover, which is as big as a large car, is also significantly larger and ten times heavier than previous Martian rovers.

Enter the Multi-Mission Radioisotope Thermoelectric Generator, or MMRTP, an energy source that relies on the heat generated by decaying plutonium dioxide to run Curiosity. It’s designed to run at least one Martian year, which is almost two Earth years.

The Curiosity is essentially a robotic science lab, equipped with sophisticated instruments for taking ground samples and analyzing their chemical make-up in the search for signs of life. This testing and communications equipment needs a lot of power to operate and needs to maintain a certain temperature to effectively operate on Mars where temperatures can go far below freezing.

The nuclear generator delivers both heat and 110 watts of steady electric power from an array of iridium capsules holding a ceramic form of plutonium dioxide. The heat is piped through the Curiosity carried by liquid Freon. Thermoelectric devices on the generator convert the heat into electricity with no moving parts. Idaho National Laboratory, which designed and tested the energy system, says it can operate for years.

Nuclear power has been used in 26 previous space missions over the past 50 years. The Idaho National Lab team began assembling the power source in the summer of 2008, which included tests for vibrations to simulate rocket launch conditions and making sure the generator’s electric field won’t affect on-board scientific instruments.