When astronaut Scott Kelly’s space capsule touched down in Kazakhstan, it was a familiar scene to Mark Kelly, who is a retired astronaut and Scott’s identical twin.
NASA is conducting a “twin study” on the brothers to explore what spaceflight does to the body. Multiple universities are involved in the research.
“We’re going to need to understand this really well before we decide to send people to Mars on an extended mission,” Mark Kelly tells NPR’s Renee Montagne on Morning Edition. For the study, he acts as a control to compare to his twin, who broke the U.S. record for longest space journey.