Scott Kelly Reveals How Living in Space Made Him Different From Twin Brother

October 31, 2017 Updated: October 31, 2017

Astronaut Scott Kelly revealed new findings from NASA’s study of how living in space changed Kelly from his twin brother on Earth.

Scott Kelly arrived back on Earth in March last year, after his year on the International Space Station. He and his brother Mark are in the middle of tests that will determine how space made Scott different—in physiology and cognitive function—from his brother. The full study will be published in three to five years, according to Scott’s interview in the Guardian.

A major find in the study is that Scott is all of 13 milliseconds younger than before he left. He was already the younger of the twins, having been born six minutes after Mark, and now he is even that little bit younger.

Other changes are more temporary. When he arrived back on Earth Scott was 2 inches taller than before. The lack of gravity in space results in a longer spine that usually returns to normal after a few months for most astronauts, according to Inverse.

The study already revealed a major genetic change in Scott.

“The one big find so far was that my telomeres, basically these things at the end of our chromosomes that shorten with stress and age, actually ended up longer than Mark’s. It’s the opposite of what the scientists expected, given the challenging environment on the ISS, exposure to radiation, etc,” Scott told the Guardian.

PBS revealed there are upsides and downsides to longer telomeres. The upside is that signs of aging slow down or remain stable. The downside is that longer telomeres combined with increased radiation, like that which someone would experience in space, can result in higher risk of an aggressive form of cancer. Kelly’s telomeres have reportedly shrunk back to normal.

In addition to the physiological effects of returning from space travel, including reduced blood cells that will take six to eight months to return to normal and other reactions as the body adjusts itself back to life within the Earth’s gravitational pull, there is also a period needed for psychological recovery.

“The psychological effect, at least for me, being in this controlled environment and being told what to do and when to do it for a year, and then coming back and not having that type of structure, it’s definitely a challenge,” said Scott.

Scott just published a book “Endurance: A Year in Space, a Lifetime of Discovery” that talks about his time aboard the International Space Station. He hopes the book can give readers a sense of being there, especially when he went on spacewalks. He said his time in the Navy prepared him to keep organized and focused.

“There are so many little tasks to take care of on a spacewalk—eight hours is barely enough time to complete everything we’re assigned. So I just kept focused on what was in front of me: my gloves, the pieces of the station in front of me. I barely even looked at the Earth looming just outside my field of vision,” he said.

As far as his favorite moment in the entire process, Scott reveals its the moment he came back. “Coming back from space after a year. Just the smell after the Soyuz hatch opened. I can’t imagine a better feeling.”