When the Apollo astronauts climbed into the command module as they approached Earth, they left the suitcase behind in the lunar module; then they fired the lunar module’s engines to divert it to the area over the Tonga Trench, one of the deepest parts of the Pacific—so the cask would fall into the sea and sink to the bottom. In the decades since, no excess radioactivity was ever detected, which means the protective shell did its job. The cask of plutonium lies on the floor of the Pacific to this day. The plutonium is about half-decayed by now, but it’s still producing over 800 watts of heat as
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