The International Space Station (ISS) has sprung a leak after being hit by space junk or a micrometeorite.
Mission flight controllers in Houston and Moscow noticed a drop in pressure on Wednesday night and, after a search on Thursday, astronauts discovered a 2mm hole in the Russian section of the station.
At that size it would have taken just 18 days for the crew to run out of air if they had not spotted the leak.
The damage was found by closing hatches to each module one at a time, and European Space Agency (ESA) astronaut Alexander Gerst initially plugged the gap with his finger, before using duct tape to cover the hole, preventing more air leaking into space.
During a live feed from the ISS, Nasa's ground control were heard to comment: "Right now Alex has got his finger on that hole and I don't think that's the best remedy for it."
The International Space Station’s cabin pressure is holding steady after a repair was made to address a leak on a Russian Soyuz spacecraft that had caused a minor reduction of pressure. More... https://t.co/qgxgPrtPDEpic.twitter.com/QQozo48sOP
— Intl. Space Station (@Space_Station) August 30, 2018
Later, the two Russian spacemen put sealant on a cloth and stuck it over the area, while their colleagues took photos for engineers on the ground. Flight controllers, meanwhile, monitored the cabin pressure while working to come up with a better long-term solution.
Mission Control outside Moscow told the astronauts to let the sealant dry overnight and that more leak checks would be conducted on Friday. The makeshift repairs seem to have stabilised the situation, at least for now, officials said. Earlier, flight controllers tapped into the oxygen supply of a Russian cargo capsule to partially replenish the atmosphere in the station.
A spokesman for the ESA said: “Last night International Space Station mission control noticed a reduction of pressure. This morning the crew gathered in the Russian segment of the Space Station before searching for the cause of the pressure change.
“Working with mission control in Houston, USA, and Moscow, Russia, the astronauts localised a leak that appears to be in the Russian segment. The crew are working through troubleshooting and repair procedures.
“The crew are healthy and safe with weeks of air left in the International Space Station reserves.”
The damage is believed to have occurred when a micrometeorite or piece of space debris hit the station.
Experts have warned for several years that the amount of junk orbiting the Earth, from defunct satellites and spacecraft poses a grave danger to the ISS. But this is the first time any significant damage has been caused.
Since 1957, more than 5,250 launches have led to more than 23,000 tracked objects in orbit around Earth.
But only about 1,200 are working satellites – the rest are debris and no longer serve any useful purpose.
Many derelict craft have exploded or broken up, generating an estimated 750,000 pieces larger than 1 cm and a staggering 166 million larger than 1 mm spinning round the globe at 30,000 mph.
Last year the ESA appealed to satellite operators and space agencies to clear up their retired crafts warning that pieces of space junk had "tremendous relative velocities, faster than a bullet, and can damage or destroy functioning space infrastructure".
In March a prototype space "litter picker" designed by the University of Surrey was sent to the ISS. The tiny spaceship will perform two experiments to deploy and then capture a small ‘cubesat’ satellite, first using a net, and then using a harpoon. If it works it could be sent up to clear Earth’s orbit of dangerous debris.
As well as Gerst, there are five other astronauts on board. Commander Drew Feustel, FlightEngineers Ricky Arnold and Serena Auñón-Chancellor of NASA, and Oleg Artemyev and Sergey Prokopyev of the Russian space agency Roscosmos, gathered in the Russian segment of the station and, after extensive checks, reported that the leak appears to be on the Russian side of the orbital outpost.
There is currently a Russian Progress cargo ship docked at the ISS and Roscosmos is recommending using oxygen from its tanks to repressurise the station.
A spokesman for Nasa said: “Programme officials and flight controllers are continuing to monitor the situation as the crew works through its troubleshooting procedures.”