Nasa's Scott Kelly back down to Earth after 340 days spent in space
Throughout their nearly year-long stay in space, Kelly, 52, and Mikhail Kornienko, 55, were the subjects of dozens of medical experiments and science studies into weightlessness, and into how the high-radiation environment of space affects the human body.
The research will help the US space agency, and its partners, to send humans to Mars for at least two years.
