The International Space Station, photographed by an astronaut aboard the space shuttle Endeavour on Feb. 10, 2010.

Scientists have detected living bacteria "from outer space" in samples collected from the exterior of the International Space Station (ISS) during spacewalks, cosmonaut Anton Shkaplerov told Russia's state-owned TASS news agency.

These spacewalks were conducted by cosmonauts, who collected material from the Russian part of the ISS using cotton swabs, which were sent to Earth for analysis, Shkaplerov said.

"And now it turns out that somehow these swabs reveal bacteria that were absent during the launch of the ISS module," Shkaplerov told TASS. "That is, they have come from outer space and settled along the external surface. They are being studied so far, and it seems that they pose no danger."

In the brief TASS report, Shkaplerov does not elaborate on how the Russian researchers arrived at their extraterrestrial conclusion. As CNET notes, it seems like Earthly contamination would be tough to rule out, given how hardy many microorganisms tend to be. Some bacteria, and tiny micro-animals known as tardigrades, have demonstrated the ability to survive for extended periods in the harsh conditions of space.

And terrestrial organisms may have accidentally made their way to the ISS before, if a controversial 2014 claim by Russian space officials is to be believed. Back then, space station official Vladimir Solovyov announced, also via TASS, that sea plankton and other microorganisms had been spotted in cosmonauts' spacewalk samples.

The sea-plankton claim, and that of Shkaplerov, are based on Russian research, so NASA doesn't have much to say about them. Indeed, a NASA spokesman referred questions about Shkaplerov's space bacteria to Roscosmos, the Russian federal space agency.

Shkaplerov has served two stints aboard the ISS and is set to launch on his third mission next month.

You can read the full TASS story here: http://tass.com/science/977591

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