The two men will spend a year aboard the International Space Station. Courtesy: NASA.
Two astronauts will soon begin training for a year-long mission on the International Space Station.
NASA's Scott Kelly and the Russian Federal Space Agency's Mikhail Kornienko will launch in 2015, and return twelve months later in 2016.
NASA says the mission is specifically designed to study how the human body reacts to long-term spaceflight, ahead of planned space missions beyond earth orbit, including potentially to Mars.
"The one-year increment will expand the bounds of how we live and work in space and will increase our knowledge regarding the effects of microgravity on humans as we prepare for future missions beyond low-earth orbit," NASA official William Gerstenmaier said in a statement.
Both men are old hands at spaceflight.
Kelly flew two space shuttle missions, once as pilot and once as commander, and served as flight engineer and later commander on two International Space Station
expeditions. Those four missions accounted for more than 180 days in space.
Kornienko has been involved in the space industry since 1986, training as a backup crew member for one ISS expedition and serving as a flight engineer on two others. He's spent 176 days in space.
The astronauts will be used to study the effects on microgravity on bone density, muscle mass, strength, vision and other physical attributes.
The tests will be key in helping humans adapt to long-term space flight, especially missions to Mars and other inner Solar System bodies, which could last several years.
Twelve months may sound like a long time in space, but it's not quite the record.
Russian cosmonaut Valeri Polyakov spent 437 days aboard Russia's Mir space station between 1994 and 1995.