Plankton 'hitched a ride to space'

In a discovery that has baffled scientists Russian cosmonauts say they have found plankton thriving on the surface of the International Space Station (ISS).

According to Russian chief of the ISS orbital mission Vladimir Solovyev, cosmonauts collected the samples while cleaning the surface of the Russian section of the space station.

"We found traces of sea plankton and microscopic particles on the illuminator surface ," Solovyev told Russian news agency ITAR-Tass.

He said the plankton was not native to the ISS launch site in Baikonur, Kazakhstan, and its presence was probably due to "uplifting air currents which reach the station and [deposit the plankton] on its surface", 420km above the Earth .

Scientists concede that it is also possible that the plankton hitched a ride from Earth when the space station modules were launched.

The finding supports research by Russian space agency Roscosmos that suggests that tiny microorganisms, known as extremophiles, are able to survive in space.

But other scientists are sceptical.

"I would be surprised if any form of life were able to survive in space," said Professor Charles Griffiths, of the University of Cape Town's zoology department.

"It is a vacuum, so there would be no water and no oxygen, the two things that are essential to sustain life."

But Professor Chandra Wickramasinge, of the Buckinghamshire Centre for Astrobiology, claims that the discovery of plankton on the ISS supports the theory that life did not develop independently on Earth but migrates continually from one inhabitable planet to another by means of interplanetary cross-contamination, or "panspermia".

Wickramasinge said that algae-like organisms called diatoms had previously been found on meteorites which had fallen to Earth.

"Diatoms have been found on meteorites in Sri Lanka but there has been no proof where they came from.

"This is the first time that we have evidence that points towards complex living organisms falling from the skies to Earth.

"The space station is orbiting the Earth in a total vacuum. So it is a total defiance of the laws of physics to say these organisms were blown into space from Earth," said Wickramasinge.