A Soyuz capsule carrying Nasa astronaut Scott Kelly and Russian cosmonauts Mikhail Kornienko and Sergey Volkov landed in Kazakhstan on Wednesday (2 March). The landing took place on a steppe near the Kazakh city of Zhezkazgan at 10.26am local time.

Kelly and Kornienko had been aboard the space station for 340 days, about twice as long as previous crews. Their flight sets a record for the space station and for the longest US space mission. The men hugged their crewmates goodbye and floated inside their Soyuz capsule at 4.43pm EST, along with Volkov, who had been in space for five-and-a-half months.

Throughout their nearly year-long stay in space, Kelly, 52, and Kornienko, 55, have been the subjects for dozens of medical experiments and science studies designed to learn more about how weightlessness and the high radiation environment of space impact the human body. The research is intended to help the US space agency and its partners develop plans for eventual human missions to Mars that will last at least two years.

Kelly, along with his identical twin brother Mark Kelly, a former Nasa astronaut, are also participating in genetic studies, the first to assess if genetic changes take place during long spaceflights. Kelly's 340-day mission eclipses the previous US record-long spaceflight of 215 days set by former astronaut Michael Lopez-Alegria aboard the space station in 2007.

The world's longest missions were made by four Soviet-era cosmonauts aboard the now-defunct Mir space station, including a January 1994 to March 1995 flight spanning nearly 438 days by record holder Valeri Polyakov, a physician.