10 Ways Space Changes the Body

Former astronaut Mark Kelly (left) poses with his identical twin brother, astronaut Scott Kelly (right). As part of NASA’s Twins Study, Scott spent nearly a year in space, while Mark stayed here on Earth. This gave researchers a chance to study the health effects of long-term spaceflights. (Credit: NASA) Scott and Mark Kelly are identical twin brothers. Though that alone does not make them unique, what does is the fact that they are also both astronauts. In order to take advantage of the Kellys’ unique situation, NASA scientists decided to conduct a detailed study on the twins, aimed at unraveling how nature versus nurture plays out in space. As part of NASA's Twins Study, researchers collected biological samples from each of the Kellys before sending Scott to the International Space Station for a year starting in March 2016. Meanwhile, his brother Mark, who retired as an astronaut in 2011, remained ...