NASA In this image from Dec. 8, 2017, four reindeer walk past the Balloon Array for Radiation-belt Relativistic Electron Losses, or BARREL, payload on the launch pad at Esrange Space Center near Kiruna, Sweden. BARREL primarily measured X-rays in Earth’s atmosphere near the North and South Poles. These X-rays are caused by electrons that rain down, or precipitate, into the atmosphere from the giant swaths of radiation that surround Earth, called the Van Allen Belts. Understanding this radiation and its interaction with Earth’s atmosphere helps us to learn about planetary…
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