By Brian Vastag
The Washington Post
WASHINGTON — Happy accidents litter the annals of scientific discovery.
Here’s another: NASA probes that are exploring the treacherous twin Van Allen radiation belts encircling the Earth spied a third, unexpected band of radiation that burst into view and then disappeared, scientists report Thursday.
The NASA probes spotted the temporary band of high-energy electrons just three days after launch.
The discovery has stunned scientists and is forcing a rethink of the radiation environment above Earth, with implications for proposed human deep-space missions.
In 1958, early NASA satellites recorded two zones of dangerous electron and proton radiation extending 12,000 miles beyond Earth. Named for scientist James Van Allen, the dual donut-shaped regions were the first major discovery of the space age.
Last Aug. 30, NASA launched the twin Radiation Belt Storm Probes - since renamed the Van Allen Probes - to provide a deeper understanding of the region. A radiation-detection instrument was scheduled to be switched on a month later, but mission scientists decided to turn it on early.
Three days after launch, and just a day after the instrument powered up, the third belt appeared.
“We initially thought, ‘This looks odd, maybe something’s screwed up with our instrument,’” said Shri Kanekal, a mission scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md. “But as days went by [the third belt] just stood there. We checked our instrument and became more and more confident there was not something wrong.”
The third belt, which formed between the two known belts, disappeared about a month later when a blast of energy from the sun blew past Earth. Such solar weather can warp and compress the outer Van Allen belt, but earlier missions had never seen a third belt form.
Researchers are now puzzling over the temporary band of high-energy electrons. They’re trying to understand why it did not quickly merge with the outer belt, as predicted by current understanding of the physics of the region.