World

American astronaut Scott Kelly, 2 Russians heading to space station for 1 year

  • Russia's Soyuz-FG booster rocket with the space capsule Soyuz TMA-16M that will carry a new crew to the International Space Station (ISS) is installed at the launch pad in Russian leased Baikonur cosmodrome, Kazakhstan, Friday, March 27, 2015. The new Soyuz mission is scheduled for Saturday, March 28.(AP Photo/Dmitry Lovetsky)

    Russia's Soyuz-FG booster rocket with the space capsule Soyuz TMA-16M that will carry a new crew to the International Space Station (ISS) is installed at the launch pad in Russian leased Baikonur cosmodrome, Kazakhstan, Friday, March 27, 2015. The new Soyuz mission is scheduled for Saturday, March 28.(AP Photo/Dmitry Lovetsky)  (The Associated Press)

  • Russian cosmonauts  Mikhail Korniyenko, crew member of the mission to the International Space Station, ISS, speaks during a news conference in the Russian leased Baikonur cosmodrome, Kazakhstan, Thursday, March 26, 2015.  The start of the new Soyuz mission is scheduled on Saturday, March 28.(AP Photo/Dmitry Lovetsky)

    Russian cosmonauts Mikhail Korniyenko, crew member of the mission to the International Space Station, ISS, speaks during a news conference in the Russian leased Baikonur cosmodrome, Kazakhstan, Thursday, March 26, 2015. The start of the new Soyuz mission is scheduled on Saturday, March 28.(AP Photo/Dmitry Lovetsky)  (The Associated Press)

  • Russian cosmonaut Gennady Padalka, crew member of the mission to the International Space Station, ISS, attends a news conference in Russian leased Baikonur cosmodrome, Kazakhstan, Thursday, March 26, 2015. The start of the new Soyuz mission is scheduled on Saturday, March 28. (AP Photo/Dmitry Lovetsky)

    Russian cosmonaut Gennady Padalka, crew member of the mission to the International Space Station, ISS, attends a news conference in Russian leased Baikonur cosmodrome, Kazakhstan, Thursday, March 26, 2015. The start of the new Soyuz mission is scheduled on Saturday, March 28. (AP Photo/Dmitry Lovetsky)  (The Associated Press)

An American astronaut and two Russian cosmonauts are to blast off early Saturday to begin a year away from Earth.

Of the three-man team, American Scott Kelly and Russian Mikhail Kornienko are to stay at the International Space Station until March 2016. Their trip is NASA's first stab at a one-year spaceflight, anticipating Mars expeditions that would last two-to-three years.

Kelly, Kornienko and another Russian, Gennady Padalka, will begin their marathon mission with a Soyuz rocket launch from Kazakhstan and are to arrive at the orbiting outpost six hours later.

Kelly's identical twin Mark, a retired astronaut, agreed to take part in many of the same medical experiments as his orbiting sibling to help scientists see how a body in space compares with its genetic double on Earth.