the Cassini space probe—containing more deadly plutonium [72.3 pounds of Plutonium-238] than had ever been used on a space device—was launched 20 years ago. And this past weekend—on Earth Day—the probe and its plutonium were sent crashing into Saturn.
Cassini didn’t have the propulsion power to get directly from Earth to its final destination of Saturn...So NASA [in 1999] had Cassini come hurtling back at Earth at 42,300 miles per hour and skim over the Earth’s atmosphere at 727 miles high. If there were a rocket misfire or miscalculation and the probe made what NASA in its “Final Environmental Impact Statement for the Cassini Mission” called an “inadvertent reentry,” it could have fallen into Earth’s atmosphere, disintegrating, and releasing plutonium. Then, said NASA in its statement, “Approximately 7 to 8 billion world population at a time … could receive 99 percent or more of the radiation exposure.”