Mars Curiosity Radioisotope General Purpose Heat Source (GPHS) Units

A stack of General Purpose Heat Source (GPHS) units awaits assembly and integration into the Mars rover Curiosity. This power system, known as a Multi-Mission Radioisotope Thermoelectric Generator (or MMRTG), produces a dependable flow of electricity using the heat emitted from the natural radioactive decay of plutonium oxide as its "fuel."