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。
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。
As the plutonium-238 that served as the Pioneers' onboard heat source radioactively decayed, it would have emitted less heat over time.
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