Astronaut Twins Begin Unprecedented One-Year NASA Study

NASA astronaut Scott Kelly (right) and his twin brother Mark. Credit: Robert Markowitz/NASA NASA is about to take yet another bold step toward sending humans to Mars. At 3:42pm Eastern time tomorrow afternoon, NASA astronaut Scott Kelly will strap into a Russian rocket and kiss Earth goodbye for an entire year to live on the International Space Station. Meanwhile, his identical twin Mark, a retired NASA astronaut himself, will stay here on Earth. Both men, though serving on vastly different fronts, are the guinea pigs in a big-time NASA study that will examine the physical and psychological effects of extended stays in space. By comparing changes in the bodies of the 51-year-old men, scientists hope to learn what it will take to safely send humans to Mars, a seven-month undertaking just in travel time.