© David Filipov/The Washington PostA city near the Ural Mountains in Russia that might be the origin of the radioactive cloud released in September.
Remember that harmless radioactive cloud that mysteriously drifted across Europe back in September? Turns out it may indeed have come from Russia after all - from an area that had radioactivity of about 1,000 times higher than normal, as officials there acknowledged for the first time Tuesday. Experts emphasized that the unusually high levels may still have been harmless.
What remains a mystery, however, is what produced this cloud. The most likely culprit, a serial offender nuclear reprocessing plant, still denies any connection.
It was Austria that first detected unusually high levels of radiation Oct. 3, with Germany confirming them the next day. Over the next two weeks, the levels went up and down and finally faded away over a vast swath of the continent.
France's
Institute for Radiological Protection and Nuclear Safety calmed fears this month, saying that the cloud of radioactive isotopes - Ruthenium-106 - had posed no health hazards. But the French researchers remained baffled by the cloud's origins, and over the next few weeks,
they calculated that it most likely came from deep inside Russia. Germany's governmental Agency for Radiation Protection came to the same conclusion.
Comment: You can read more about the spike in radioactivity over Europe in September and October here. Bear in mind that the same thing happened already in January and February, except that back then the source was suspected to be somewhere near the Arctic Circle.