A Russian cosmonaut claims to have caught aliens. Cosmonaut Anton Shkaplerov says he found bacteria clinging to the external surface of the International Space Station that didn't come from the surface of Earth. 

Shkaplerov told the Russian news agency Tass that cosmonauts collected the bacteria by swabbing the outside of the space station during space walks years ago.  

"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."

The cosmonaut is preparing for his third trip to the space station next month. The collection of life forms from the outside of the ISS during one of his previous trips was something of a mini controversy a few years back. Russian scientists reported that spacewalk sample harvests yielded evidence of apparent sea plankton clinging to the station. The claims caught NASA by surprise at the time, which said it had heard nothing from the Russians about any space plankton.

NASA has also yet to chime in about the apparent extraterrestrial bacteria from outer space hanging out on the surface of the ISS that Shkapkerov claims to have knowledge of. I reached out to the on-earth offices of NASA's space station program for more information and will update this post when I hear back.

It seems unlikely that anyone could completely rule out that the bacteria have Earthly origins. We know that bacteria and other life forms like tardigrades can live in extreme conditions like those in space, so it's possible that undiscovered microbes living in Earth's upper atmosphere were picked by the space station over the years.

In fact, a recent study purports that high-speed flows of "space dust" could actually launch just such microbes on journeys from Earth to other worlds. Perhaps some bacteria decided to skip that long trip and just took up residence on the space station instead. After all, a visit to the ISS is known to be productive for other lower life forms, like this worm that grew an extra head after its visit.