LOS ANGELES (February 28, 2013)—An extra ring of radiation encircled the Earth for a few weeks last year.
There are usually two doughnut-shaped rings of highly charged particles encircling the planet.
They were discovered in 1958 and they're known as the Van Allen radiation belts.
But NASA's recently launched twin satellites to the treacherous region discovered a third, temporary ring that appeared for a month before a shock wave from the sun destroyed it.
Scientists are still trying to figure out how often this happens.
The twin spacecraft launched last year on a mission to explore the Van Allen belts.
Solar storms can cause the rings to expand, posing a potential threat to satellites.
The discovery was reported online Thursday in the journal Science.