As the plutonium-238 that served as the Pioneers' onboard heat source radioactively decayed, it would have emitted less heat over time.
为先驱者号们提供舱内热动力源的钚238会有放射性衰变，其发射量会随着时间的推移而越来越小。
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It will have solar panels and a supplementary power source in the form of a plutonium-238 nuclear battery, the same type installed on the forthcoming Mars Science Laboratory rover.
Curiosity is a beast of a rover, weighing one ton, measuring ten feet long by seven feet tall (at the top of the mast), and powered by a plutonium-238 fueled electrical generator.