Scott Kelly Return After a Year in Space

The mission is a record for the ISS and will give Cmdr Kelly a tally of 520 cumulative days in space, over four flights.

The harsh space environment takes its toll in the form of muscle atrophy, sleep problems, bone loss, vision impairment and radiation exposure. But some of the most pronounced effects are on the mind.

Before landing, Cmdr Kelly told reporters during a live link-up: “Physically I feel pretty good… but the hardest part is being isolated in the physical sense from people on the ground who are important to you. There’s a loss of connection.”

From Kazakhstan, Cmdr Kelly will be flown to Houston in the US, where researchers at the US space agency (Nasa) will begin a series of scientific checks.

Mark Kelly, who was an astronaut, now retired, has been undergoing tests of his own on Earth during his brother’s sojourn on the ISS.

Comparisons between the twins should allow scientists to deepen their understanding of the subtle physical and psychological shifts that occur during long stays on orbit.

Nasa says the research should inform its stated aim of one day sending humans to Mars.