Year-long space trip is 'a rehearsal for Mars'
After the best part of a year in space and a re-entry which subjected his body to more than four times gravity's earthly pull after 340 days of weightlessness, Scott Kelly might have been forgiven yesterday for wanting a hard-earned rest.
But within minutes of a blackened Soyuz capsule carrying him and two Russian colleagues from the International Space Station (ISS) landing on the icy steppe of Kazakhstan, the Nasa astronaut was made to run around an obstacle course.
Commander Kelly explained: "We go through about an hour of field tests of various kinds - one is even like an obstacle course, where you run around, stand up from a sitting position and jump."
Such is life when, as one of his colleagues at America's space agency put it, your role is to be a "living, breathing, walking medical specimen".
Kelly returned to Earth in the early hours after the longest stay in space by an American (the overall record of 437 days is held by Russian Valeri Polyakov), which encompassed both routine cosmos-based duties - fixing ammonia cooling systems and routing cables for docking ports - and a very particular role as a guinea pig for humanity's eventual effort to reach Mars.
The 52-year-old and his Russian colleague, Mikhail Kornienko, had been the subject of dozens of medical and scientific experiments during their stay on the ISS, to further examine how the body responds to weightlessness.
The research - which includes a unique comparative study between Kelly and his earthbound identical twin brother Mark - is designed to help Nasa prepare for the physical and psychological demands that will be made of the crew of a Mars mission, which would last an estimated 30 months. The American space agency has set the 2030s as the target for its first manned mission to the Red Planet.
In order to make such a journey even feasible, scientists need to find ways to counter some of the effects that long-term exposure to weightlessness is known to have on astronauts, such as the upward redistribution of fluid around the body.
The phenomenon has a number of negative effects, ranging from a puffy face to the heart having to pump a higher volume of liquid, to increased pressure on the eyeball which can cause problems with vision and, in worst cases, blindness.