Russian Cosmonauts Wrap Up Spacewalk

The outing was the 188th in support of the space station and the 10th of Gennady Padalka's career, a veteran cosmonaut and grandfather who is serving as commander of the ISS.

In June, Padalka, 57, set the world record for the most time spent in space with a total of 803 days.

His spacewalking partner was Mikhail Kornienko, 55, undertaking his second walkabout in space.

Hours into the rigorous spacewalk, Padalka and Kornienko playfully taunted each other over whose hands were coldest and who had the most spirit, according to live footage broadcast on the websites of the Russian and US space agencies.

The spacewalk was over at 7:51pm GMT, an hour ahead of schedule. It lasted a total of five hours and 31 minutes, Nasa said.

Padalka and Kornienko installed devices - known as gap spanners - on the hull of the station to help "facilitate the movement of crew members on future spacewalks," Nasa said.

They also cleaned windows, installed fasteners on communications antennas, replaced an aging antenna used for the rendezvous and docking of visiting vehicles at Russian docking ports, and took pictures of locations and hardware on Zvezda and nearby modules.

Floating against the bright blue oceans and white clouds of Earth, the astronauts filmed the outing with small handheld cameras, constantly communicating with each other and Russian mission control outside Moscow.

Once they get out of their spacesuits, they will be able to sample their first bites of space-grown red romaine lettuce that their colleagues have saved for them.

Two US and one Japanese astronaut tasted the lettuce earlier in the day Monday.

Nasa astronaut Kjell Lindgren described the leafy greens as "awesome."

Scott Kelly, who is spending one year aboard the ISS with Kornienko, said the leaf tasted a bit like arugula.

The ability to cultivate food during a trip to Mars in the coming decades will be key to surviving the trip, which could last months or years.

"This payload, and having the ability for us to grow our own food is a big step in that direction," Kelly said.

The next spacewalk around the Russian section is set for January or February 2016, space industry official Alexander Kaleri told TASS state news agency on Monday.