Scott Kelly

TIME 100 2015 Scott Kelly
Marco Grob for TIME

Marathon man

Scott Kelly’s yearlong mission aboard the International Space Station is indeed worthy of special note and attention. We need to know much more about human reaction to long-term spaceflight before any deeper exploratory missions can be planned. But what may be of greater significance to all of us here on Earth is research into the remarkable similarities between how the body changes in zero-G and how it changes as a result of ordinary aging. If we learn more about one, we could apply that same knowledge toward arresting both. We started this type of research when I returned to space in 1998, and I am very glad it is being continued with this mission. Scott’s willingness to devote a year of his life in cooperation with his identical twin brother Mark, who will remain on Earth, may have a profound impact on all of us.

Former Senator Glenn was the first American to orbit the earth

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