British astronaut Tim Peake, who was embarking on his first ever spacewalk, checked his colleague's appearance while they were outside the International Space Station and described what he saw as a "film of water".

"Today's exhilarating #spacewalk will be etched in my memory forever - quite an incredible feeling!" he said, later posting the photo to Twitter.

Tim Peake takes some big steps for British astronauts.

Major Tim tweeted his appreciation to Phil Collins

The discovery of water in the helmet of a USA astronaut brought an early end to a spacewalk Friday at the International Space Station, NASA said.

The day prior, Peake wrote of his excitement and anticipation for the event, which followed "several years of training".

Originally scheduled for six-and-a-half-hour to switch out an electrical component in the ISS' solar power system, the spacewalk was curtailed to four-hour-and-43-minutes on Friday after NASA's Timothy Kopra reported the malfunction, the United States space agency said in a statement.

Peake, in particular, received a bounty of well wishes — from space as well as Earth.

The astronauts waiting anxiously inside pulled off Kopra's helmet, then measured the water that had leaked, presumably from the suit's cooling system. Mission Control informed the astronauts everything looked good.

The leak had increased as Peake and Kopra returned to the airlock within 15 minutes. It's explored all over the world.

Major Peake replied "It's great to be wearing it. A privilege, a proud moment".

Earlier, as Peake floated out, space station commander Scott Kelly called, "Hey Tim, it's really cool seeing that Union Jack go outside".

"With the spacewalk completed, Tim has a few days of rest before continuing work on the extensive scientific programme that is part of his six-month Principia mission". "The astronauts replaced a failed voltage regulator that caused a loss of power to one of the station's eight power channels last November, accomplishing the major objective for this spacewalk".

Peake became the first astronaut representing Britain to walk in space when he left the ISS on Friday to fix a power station problem, generating huge interest back in his homeland.