![The eight small General Purpose Heat Source blocks are stacked in a secure chamber filled with dials, gauges and valves.](https://science.nasa.gov/wp-content/uploads/2024/02/gphs-units.jpg?w=4096&format=jpeg)
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."
Credits: U.S. Department of Energy
Image CreditU.S. Department of Energy
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