By Marina Koren
In the debate over whether human beings should set off to other worlds beyond Earth, one of the most compelling cons is this: Our bodies don’t like it.
Few people know this better than Scott Kelly, the NASA astronaut who spent nearly a year on the International Space Station from 2015 to 2016. Like other astronauts, Kelly served as a test subject in the study of space travel’s effects on the human body. Unlike other astronauts, Kelly has an identical twin, Mark, an astronaut himself. This gave researchers an uncommon opportunity to monitor the two brothers as they lived in two very different environments—one on Earth and the other 250 miles above it.
According to their results, published Thursday in Science, Scott experienced a number of changes that Mark did not. Most of those changes went away after Scott returned to Earth. The long stint in space, the researchers say, produced some unexpected changes—but did not lead to any clinically significant health differences.
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