NASA spacecraft discover a third radiation belt surrounding Earth.
Within days of its launch on August 30, 2012, NASA's Van Allen Probes collected data that will rewrite textbooks. The mission consists of two spacecraft orbiting through the radiation belts encircling Earth. Scientists want to understand what causes the changing shapes of the belts—a region that can sometimes swell dramatically in response to incoming energy from the sun, posing a threat to satellites and spacecraft. Inner and outer radiation belts were discovered in 1958 with instruments on the very first U.S. satellites sent into space. But in September 2012 something happened that had never been recorded before: the particles that make up the belts settled into a new configuration, separating into three belts instead of two. The third belt lasted for four weeks, proving that the Van Allen Probes have much left to explore in near-Earth space. Watch the visualization to see what the Van Allen Probes observed.