Allure: In 2019, scientists published research that showed that astronaut Scott Kelly’s telomeres, the caps of DNA that protect our chromosomes and shorten as we age on Earth, actually grew longer while he was on a 340-day space mission compared to his grounded twin, Arizona State Senator Mark Kelly. To call the finding unexpected would be an understatement. “We were shocked,” says Susan Bailey, an associate professor in the department of environmental and radiological health sciences at Colorado State University and one of the researchers on the study published in the journal Science.

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