Legendary space explorer Aleksei Leonov died at the age of 85

The cosmonaut's death was also mourned by NASA, with the U.S. space agency interrupting its live stream of NASA astronauts Andrew Morgan and Christina Koch performing an EVA on the International Space Station in order to announce these sad news, and later tweeting that "his venture into the vacuum of space began the history of extravehicular activity that makes today's @Space_Station maintenance possible".

Leonov was also a celebrated artist who brought colored pencils to space to sketch the view of Earth. The mission is credited with kick-starting eventual worldwide cooperation aboard the global Space Station.

Russian cosmonauts and American astronauts join hands at a hotel in Athens, Greece, September 1965. From left to right, Alexey Leonov, Charles Conrad Jr. "I can still hear my breath and my heartbeat in that silence".

Leonov's 12-minute spacewalk preceded the first United States spacewalk, by Ed White, by less than three months.

British astronaut Tim Peake said Mr Leonov was "a hero to so many, pioneer of spacewalking and always full of wisdom and humour".

"When we sat at the table, they said: 'Why, that's not possible, '" Leonov recalled in 2005.

The flight and spacewalk were successful on the whole, but his return to Earth almost ended in tragedy when Mr Leonov and another cosmonaut, Mr Pavel Belyayev, crash-landed in the Siberian woods. "That worked, they opened it and drank [the borscht] and were caught by surprise". They said "Happy Birthday!" to Leonov before opening the hatch and venturing out. "I believe I never knew what the word round meant until I saw Earth from space".

Tributes poured in from across the globe, with Western space agencies and experts praising Leonov's contribution and admirers bidding him farewell.

NASA paid tribute to Leonov on Friday. These new batteries are so powerful only one is needed for every two of the hydrogen-nickel units, which will be junked.

Russian space fans were bringing flowers to his monument Friday on the memorial alley in honour of Russia's cosmonauts in Moscow.

"One of the first cosmonauts of the world space era, Alexei Leonov was committed to his Motherland and his cause, his name is lettered in gold in the world space exploration history", Roscosmos said.