It has been a long, long time, but record-breaking rocket man Scott Kelly is finally coming back to Earth. On Tuesday, the 52-year-old NASA astronaut will wrap up a 342-day mission on the International Space Station. It's not the longest jaunt in space — back in the days when Russia had its own space station, several cosmonauts pulled longer stretches and one even lasted 437 days. But it's the longest stint ever taken on the ISS, and it's the first time scientists have focused on the physical effects of such long-term spaceflight.
The hope is that studying Kelly — and his identical twin, Mark Kelly, a retired astronaut who spent the year on Earth — will help us figure out what challenges astronauts might face setting out on even longer trips, as they probably will when journeying to Mars and beyond. Doctors will check to see ...
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