Vladimir Solovyev, the official in charge of Russia’s ISS segment, told the news agency Itar-Tass that tiny plankton and microscopic organisms had been discovered on the spacecraft's exterior, describing the finds as "absolutely unique".

 

However, the truthfulness of Solovyev's claim is unclear, with Nasa refusing to confirm the story.

"As far as we're concerned, we haven't heard any official reports from our Roscosmos colleagues that they've found sea plankton," Nasa spokesperson Dan Huot told Space.com.

Dan Huot confirmed that Russian cosmonauts had been taking samples from the windows on their side of the ISS, but clarified that they'd only been looking for,

"residues that can build up on the visually sensitive elements".

 

"I don't know where all the sea plankton talk is coming from," Huot added.

Although the reports from Itar-Tass have not been confirmed, the idea of life existing in the harsh environment of space (surviving cosmic radiation, freezing temperatures and zero gravity) is quite possible.

 

 

 Tardigrades (x135 magnification):

0.18mm long, smaller than fullstops

 

 

A study in February 2013 (Microbiome of the Upper Troposphere - Species Composition and Prevalence, Effects of Tropical Storms, and Atmospheric Implications) found evidence of microbial life five to ten miles above the surface of the planet, while a type of microscopic invertebrate known as a tardigrade has even survived the vacuum of space for 10 days, shrugging radiation exposure a hundred times necessary to kill humans.

 

So while it’s possible that some sort of terrestrial life has been hanging out on the side, it’s not at all clear how - if the reports are confirmed - they got up there.

 

It could be that they arrived via some contaminated space modules but Solovyev himself suggested that they might have come from,

"rising air currents, which settle on the surface of the station".