April 11, 2019 — Long trips to space may change at least 10 key body processes, according to a first-of-its-kind study of identical twin astronauts, information that is helping NASA plan for manned missions to distant planets, like Mars.
Brothers Scott and Mark Kelly were 51 in March 2015, when Scott began his fourth and longest space mission — commanding the International Space Station (ISS) for 340 days, which set an American record. Mark, a retired astronaut who is married to former U.S. Rep. Gabrielle Giffords and is running for a U.S. Senate seat in Arizona, remained on Earth.
By comparing the two men, who share the same genes, researchers were able to see — down to the DNA — what changed as Scott endured the stresses of space travel. Scott is one of only four astronauts to have ever spent so much time in space.
The study revealed how Scott’s body changed in space. While most of those went back to normal after he returned to Earth, some have persisted for at least 6 months after his return — including changes to his eyes, to his mental abilities, and even some chromosomal damage.
Before, during, and after the mission, the men were given an array of tests. For the first report, researchers collected 317 biological samples including stool, urine, and blood. The brothers also had their physical and mental abilities regularly measured.
Some of the changes were relatively easy to explain. As Scott ate a carefully controlled diet and exercised regularly on the ISS, he lost about 7% of his body weight. Mark, who was able to eat whatever he wanted and drink alcohol, which is forbidden on the space station, gained a few pounds — about 4% of his starting weight.
One piece of good news is that most of the things that changed during Scott’s stay at the ISS — including his gut bacteria, gene expression, immune function, and metabolism — were back to normal within 6 months of his return to Earth.
A fun fact: Vaccines seem to work just fine in space. Scott got his flu shot while on the ISS, and his immune system responded much as Mark’s did. Mark got his vaccine at the same time, just back on Earth.