Charged particles trapped in planetary magnetospheres are concentrated in radiation belts. Although Earth’s radiation belts are severe enough to worry astronauts, the radiation belts that surround Jupiter are searing in comparison. In 1973 the Pioneer 11 spacecraft passed through the radiation belts of Jupiter. During its brief encounter, Pioneer 11 picked up a radiation dose of 400,000 rads, or about 1,000 times the lethal dose for humans. Several of the instruments on board were permanently damaged as a result, and the spacecraft itself barely survived to continue its journey to Saturn.