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ZHEZKAZGAN, KAZAKHSTAN - MARCH 2: In this handout provided by NASA, Russian cosmonauts Mikhail Kornienko, left, Sergey Volkov of Roscosmos, center, and Expedition 46 Commander Scott Kelly of NASA, rest in a chairs outside of the Soyuz TMA-18M spacecraft just minutes after they landed in a remote area on March 2, 2016 near the town of Zhezkazgan, Kazakhstan. Kelly and Kornienko completed an International Space Station record year-long mission to collect valuable data on the effect of long duration weightlessness on the human body that will be used to formulate a human mission to Mars. Volkov returned after spending six months on the station. (Photo by Bill Ingalls/NASA via Getty Images)

ZHEZKAZGAN, KAZAKHSTAN - MARCH 2: In this handout provided by NASA, Russian cosmonauts Mikhail Kornienko, left, Sergey Volkov of Roscosmos, center, and Expedition 46 Commander Scott Kelly of NASA, rest in a chairs outside of the Soyuz TMA-18M spacecraft just minutes after they landed in a remote area on March 2, 2016 near the town of Zhezkazgan, Kazakhstan. Kelly and Kornienko completed an International Space Station record year-long mission to collect valuable data on the effect of long duration weightlessness on the human body that will be used to formulate a human mission to Mars. Volkov returned after spending six months on the station. (Photo by Bill Ingalls/NASA via Getty Images)