American astronaut Scott Kelly, left, and Russian cosmonaut Mikhail Kornienko, play billiards at the Cosmonaut hotel in Baikonur, Kazakhstan. Photograph: Bill Ingalls/AP

Their respective countries may be going through one of the worst periods of hostility since the end of the cold war, but this week an American astronaut and a Russian cosmonaut will fly up to the International Space Station to spend a year on board together.

Despite the enmities of the cold war and the frigid relations of their governments today, scientists and astronauts from Nasa and its Russian equivalent, Roscosmos, have a fruitful and friendly history of recent cooperation. As the US government has cut space program funding, for instance, Nasa has turned to its Russian counterpart to assist with mission logistics such as sharing a launch pad.

The mission beginning this week for American Scott Kelly, 51, and his Russian counterpart Mikhail Kornienko, 54, will also feature experiments necessary to plan for a manned mission to Mars and an opportunity to compare Kellys health in space with that of his twin brother, Mark, back on earth.

Mark was also an astronaut, and is the husband of former congresswoman Gabrielle Giffords, who was shot and seriously injured in 2011.

Kelly and Kornienko will fly from Baikonur, Kazakhstan, one of the oldest launch facilities on Earth, on Friday (Saturday on the steppes).

Kelly will be the first American to spend a continuous year in space; Russian Valery Polyakov spent more than a year on the Mir space station in the 1990s.

During their year-long mission, 12 other astronauts will join them for shorter stints including Gennady Padalka, a Russian who has spent more than 700 non-consecutive days in space. Padalka will spend six months on the space station this time, after which he will have spent more days in space than any other human being.

More than 40 years after Americans landed on the moon, many in the US consider spaceflight relatively routine, but its dangers remain as destructive to human beings as ever, and sometimes as mysterious: eyeballs distended by brain fluid floating weightless around the skull, pathogens made more virulent by the variables of space, bone loss, muscle atrophy, radiation.

During their year on the ISS, Kelly and Kornienko will perform daily cognitive, visual, physical, microbial and metabolic tests, and will also keep journals that will help their respective space agencies study the psychological toll of a year in orbit.

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