The planned six-hour spacewalk by International Space Station astronauts Tim Peake of the United Kingdom and veteran space walker Tim Kopra was cut short today when Kopra developed a build-up of water in his space helmet due to a spacesuit coolant system malfunction.
NASA said neither astronaut was in immediate danger, but mission managers chose to terminate the walk for safety reasons. They would also use a syringe to collect a sample of the water and remove absorption pads from the inside of the helmet as evidence for investigators who will aim to determine the cause of the leak.
Two spacewalking astronauts - including Britain's first - have successfully restored full power to the International Space Station after replacing a broken electronic box.
Peake was able to see the water droplet within Kopra's suit describing it as "less than a golfball" in size.
Before the pioneering moment he was pictured with his Nasa colleague Colonel Tim Kopra arranging his tools and getting into the airlock.
Like rock climbers, the astronauts must always be tethered to Space Station supports. Mission Control informed the astronauts everything looked good.
He carried the unit, which would 90kg on Earth, to the far end of the space station's truss, about 60m from the exit.
"Hey Tim, it's really cool seeing that Union Jack go outside", space station commander Scott Kelly called as Peake floated free of the station.
Astronaut Tim Peake has become the first Briton to walk in space, undertaking a tricky mission to replace an electrical unit while under cover of darkness. Peake, the first United Kingdom astronaut, and Kopra arrived at the ISS in December.
Peake, in particular, received a bounty of well wishes - from space as well as Earth.
The situation brought back memories of a harrowing emergency in 2013 when Italian astronaut Luca Parmitano's helmet began rapidly filling with water and risked drowning him. The incident spurred the space agency to add absorbent pads to helmets and establish other precautions for future spacewalks - all of which came in handy on Friday.
"This is how I measure success", he tweeted, "1)crew-safe 2)main objective-completed".