Astronaut uses his thumb to plug a hole in space station

ASTRONAUTS are battling to plug a leak in the International Space Station which may have been hit by space junk or a micrometeorite.

Flight controllers in Russia and the United States first noticed a drop in pressure on Wednesday night.

The six crew on board scrambled yesterday to find the location of the leak, which was traced to a hole less than a tenth of an inch (2mm) across in the Russian segment of the orbiting space lab.

European Space Agency astronaut Alexander Gerst used his thumb to block the hole before the astronauts used electrical tape to temporarily cover it.

Although this slowed the rate of air escaping the ISS, the astronauts are working on a more long-term repair.

A statement on the station’s blog said: ‘Once the patching is complete, additional leak checks will be performed. All station systems are stable and the crew is in no danger as the work to develop a long-term repair continues.’

It is unclear if space junk or a meteorite caused the incident. But Nasa says space debris as small as 0.3mm can pose a danger to human spaceflight.

The space agency is tracking more than 20,000 pieces of space junk larger than a cricket ball and orbiting the Earth at speeds of up to 17,500mph. There are an estimated 500,000 pieces of junk the size of a marble or larger.

The University of Surrey sent a prototype space ‘harpoon’ and net to the ISS in April to try to capture some debris.

Nasa said astronauts on the station are being monitored with no early return to Earth planned for crew members.