How Does a Radioisotope Thermoelectric Generator Work? The Seebeck Effect

More than two centuries ago, a German scientist named Thomas Seebeck discovered an unexpected property of physics: Metals and some compounds are good conductors of electricity as well as heat. He found that when he combined two of these materials and then applied heat to one end while exposing the other end to cold, a small electrical voltage was created across the materials.
Today, this property, known as the Seebeck Effect, is used to power many NASA science missions that explore the most extreme environments in the solar system.