How does plutonium-238 generate electricity for spacecraft?

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radioactivity Figure 1: Radioactive decay of beryllium-7 to lithium-7 by electron capture (EC; see text).

Plutonium-238 generates electricity for spacecraft through the use of radioisotope thermoelectric generators (RTGs).1

The process relies on the alpha decay of the isotope, which releases significant thermal energy. One gram of plutonium-238 produces approximately 0.5 watts of heat. This heat is harnessed by thermoelectric devices, which utilize the thermoelectric effect in semiconductor materials to convert the thermal energy directly into electricity.213

Because plutonium-238 emits a negligible amount of gamma rays and has a relatively long half-life of 87.7 years, it is an ideal, long-lived power source for remote or unattended applications, such as space exploration missions like the Curiosity rover.241