US astronaut Scott Kelly is assisted by ground personnel shortly after landing near the town of Dzhezkazgan (Zhezkazgan), Kazakhstan, March 2, 2016.[Photo/Agencies]

CAPE CANAVERAL, Fla./ALMATY - NASA astronaut Scott Kelly and Russian cosmonaut Mikhail Kornienko returned to Earth on Wednesday after nearly a year on the International Space Station, the longest US space mission on record, intended to pave the way for human travel to Mars.

A Soyuz capsule carrying Kelly, Kornienko and Sergey Volkov, another Russian cosmonaut, made a parachute landing on the steppe near the Kazakh city of Zhezkazgan at 10:26 a.m. (0426 GMT), about 3-1/2 hours after departing the station.

Kelly and Kornienko have 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.

Volkov, who has been in space for 5-1/2 months, was the first to emerge from the capsule, to be greeted by his father Alexander Volkov, also a cosmonaut.

Kelly, extracted next, waved his hand energetically and smiled before beginning a satellite telephone conversation.

In their nearly year-long stay in space, Kelly, 52, and Kornienko, 55, have been the subjects of dozens of medical experiments and science studies trying to learn more about how the human body adjusts to weightlessness and the high-radiation environment of space.

The research aims to help the US space agency and its partners develop plans for eventual human missions to Mars that will last at least two years.