Twin astronauts Scott and Mark Kelly participated in a groundbreaking NASA study to uncover the long-term effects of space on the human body. Over nearly a year, the twins took the same medical tests — one while aboard the International Space Station and the other while back on Earth. The results, published in the journal Science, reveal that a year in space has considerable but not life-threatening impacts on the human body, offering hope that a longer-term journey to Mars is, in fact, possible in the future.

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NASA’s 4-Year Twin Experiment Takes Us Closer To Mars Than Ever Before

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