NASA has made a rather shocking discovery; there are living microbes on the outside of the International Space Station and they have no idea where they came from.
The living organisms are in fact sea plankton and while the astronauts have no idea how they got there some theories have already started appearing.
Vladimir Solovyev, chief of the Russian ISS has confirmed that there's no way the plankton could have come from the Baikonur Cosmodrone as the plankton is usually found at the bottom of the ocean.
He does, however, have another theory. "It turns out that there are some rising air currents, which settle on the surface of the station."
If it isn't being blown up from the Earth's surface than the only other explanation is that the plankton has been on the surface of the station since it was first launched into space in 1998.
This would mean the organism has been surviving in space for over 15 years, something that scientists didn't even know possible.
The discovery was made as part of a major clean-up that's taking place on the station's windows. Over the years the station's surface has become incredibly polluted due to engine flare and general wear and tear.