The best radioisotope to use in powering planet and space exploration is plutonium-239 since it has the longest half-life of 21400 years.
The half-life ofa radioactive element is the time it takes for half the amount of atoms in the element to spontaneously decay.
The half-life of radioactive elements vary.
The half life of the given radioactive elements are as follows:
Therefore, the best radioisotope to use in powering planet and space exploration is plutonium-239 since it has the longest half-life of 21400 years.
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