American astronaut Scott Kelly made a triumphant return to Earth on March 1 after spending 340 consecutive days in orbit. Not only is the length of time spent on the International Space Station remarkable—it’s the longest of any American astronaut—Kelly’s journey is also valuable to researchers because of the person he left behind on Earth: his twin brother.
While Scott was orbiting the planet, Mark, a retired astronaut, remained on Earth to supply NASA with a treasure trove of biological data. Scientists monitored both brothers before and during the yearlong mission, and will continue to do so now that the mission is over. Their research will help them better understand how space affects the human body.
“Scott Kelly’s one-year mission aboard the International Space Station has helped to advance deep space exploration and America’s journey to Mars,” said NASA administrator Charles Bolden. The information scientists gather from Kelly’s record-breaking trip could eventually help humans safely travel to Mars.
While scientists have long known that astronauts grow temporarily taller in space, thanks to fluid accumulating between the spinal discs in the lack of gravity (Scott grew 1.5 inches over the course of his voyage), there are plenty of questions about how space travel affects the metabolism, psychology and genes of astronauts. Researchers took blood samples, body scans and swabs of DNA from the Kelly brothers to measure bone loss, muscle mass and even the shape of the men’s eyeballs. The last of these tests was suggested after previous astronauts reported their vision had deteriorated after spending time in space. Scientists hypothesized the shape of astronauts’ eyes changes because the volume of blood in the upper body increases without gravity acting on the body. NASA will also use the Kelly brothers to study how the body reacts to radiation exposure, weightlessness, stress and isolation during long-duration spaceflight. So what makes twins—especially monozygotes (identical twins) like the Kelly brothers—so valuable in this kind of study? It’s their shared genes. Since both men started off with the same genetic material, any changes in their health and anatomy can be attributed solely to the environment. This concept is called epigenetics, and by using it to compare the genes of the Kelly twins, researchers will be able to see the direct impacts prolonged space travel has on the genome. The only downside to NASA’s study of the Kelly twins is their extremely limited sample size of two. Also, the brothers did not follow the same diet over the past year, and food is known to influence the gut microbiome. While in space, Kelly and his Russian counterpart, Mikhail Kornienko, conducted almost 400 investigations on other subjects. They captured images of Earth from space, since their orbital path covered more than 90 percent of Earth’s population. They tested a network that could operate swarms of spacecraft and they used a new instrument to study dark matter. During their year aboard the space station, the men welcomed six resupply spacecraft, including SpaceX’s Dragon and Orbital ATK’s Cygnus. Kelly also got the chance to stretch his legs, venturing outside three times for spacewalks.
Back on the grid! Returned from #spacewalk and my computer was down. Real-life lesson in importance of connectivity. #YearInSpace #spacewalk #latergram #connectivity #iss #space #spacestation A photo posted by Scott Kelly (@stationcdrkelly) on
But of course the most important data might not be uncovered until Scott has been back on Earth for a while. NASA is collaborating with Johns Hopkins, Cornell University, Stanford University and Colorado State University for their ongoing health studies of the Kelly twins.
The studies will mark the end of Scott’s career with NASA. After this last trip to space, he announced his retirement, effective April 1, though he will continue to undergo periodic health tests and provide medical samples
“We need to figure out how people are going to live in space for really long periods of time,” said Mark Kelly before his brother left for the yearlong mission. “Especially if we want to send somebody to Mars or maybe we want to build a base on the moon.”