LULU GARCIA-NAVARRO, HOST:
Now to a mystery in the skies over Europe - in October, scientists across the continent who monitor the atmosphere reported detecting small amounts of a radioactive isotope. It's known as ruthenium-106. The levels weren't dangerous. But they were surprising because this isotope isn't normally there. NPR science editor Geoff Brumfiel has been following this strange event. And he joins me in the studio. Hey.
GEOFF BRUMFIEL, BYLINE: Hi, Lulu.
GARCIA-NAVARRO: OK. So what is ruthenium-106, and where does it come from?
BRUMFIEL: Well, it is a radioactive isotope with a half life of a little over a year. And that's notable because that means that it isn't really found in nature. It decays away very quickly. Where it is found is inside nuclear reactors. And so normally, you only see it when something goes very wrong. In fact, the last time it was detected in Europe was after the Chernobyl disaster in 1986.
GARCIA-NAVARRO: OK, that doesn't sound good. Are researchers worried?
BRUMFIEL: I think when they first saw it they were on edge because, remember, in Chernobyl, there was no official announcement. So actually, ruthenium was one of the first clues that something had gone wrong. But this unfolded very differently. So first off, there was never much ruthenium in the air. It wasn't dangers. It was tiny, tiny amounts. And second, the ruthenium was all they saw. They never saw like other radioactive isotopes that you might see if there was a nuclear power accident.
GARCIA-NAVARRO: OK, so what is going on? What are the suspects?
BRUMFIEL: Well, the International Atomic Energy Agency received reports from 43 countries that saw this ruthenium. And I should say it's now gone. It's dissipated. Those countries all said they saw it. But they also all said, we didn't do it.
GARCIA-NAVARRO: We didn't do it. OK.
BRUMFIEL: It's a classic case of everyone smelled it and no one dealt it. So basically, you know, there's no declaration of an accident. But many Western scientists are suspecting Russia. And there are a couple of reasons why.
GARCIA-NAVARRO: This sounds like every conversation I always have here.
BRUMFIEL: I know. It all goes back to Russia.
BRUMFIEL: Well, actually, in this case, it literally goes back to Russia. Because what they did was they took all the detection data they had, and they took their meteorological models. And they ran everything backwards. And you know, the cloud looked like it probably came from somewhere between the Volga River and the Ural Mountains in sort of central, slightly western Russia. So that would serve as their first clue.
The second clue is that ruthenium-106, it turns out, is sometimes chemically isolated in the process of making isotopes for medical purposes, for medical imaging and things. So basically, what they think is that if there was a facility that was doing that kind of work maybe they had some sort of incident. Well, there's - there is a facility in that area. It's called the Research Institute of Atomic Reactors. It's in a city called Dimitrovgrad. Now, my colleague Alina Selyukh and I reached out to that institute. They say, nope, no problem here, nothing to see. It still remains sort of the chief suspect. But this is really circumstantial evidence. There is not a lot here to sort of hang your hat on.
GARCIA-NAVARRO: So will this mystery ever be solved?
BRUMFIEL: Well, it's no longer detectable. And there aren't really anymore clues. So I think honestly unless someone just comes out and says, you know...
GARCIA-NAVARRO: ...I did it.
BRUMFIEL: ...I did it - my bad, we may never know.
GARCIA-NAVARRO: That's Geoff Brumfiel, radioactive mystery editor here at NPR. Thanks for coming in.
BRUMFIEL: Thanks, Lulu.
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