Studying Scott Kelly: What 340 Days in Space Can to Your Body, Mind, and Genes

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Astronaut Scott Kelly spent more than 340 days on an extended deployment to the International Space Station, setting a record for the longest stay in space by a U.S. astronaut. His twin brother, Mark, meanwhile stayed earthbound. In doing so, he helped to set up the control for a massive NASA study looking to learn more about how long-term space travel affects the human body.

Now, NASA has shared early results of the groundbreaking study and, it seems, 340 days of floating can have substantial effects on the body and mind. While the data still has months of analysis to undergo, information released this week showed some notable changes to Scott's body. 

The most obvious (and expected) changes were noticed in areas like bone and muscle mass (both decrease in space) as well as some changes in circulation in eyesight.

But the easily observable outward changes are now joined by changes at the molecular level as well. In Scott Kelly’s DNA, those changes included lengthening of telomeres, or “the protective caps on the ends of their chromosomes,” as well as reduced levels of DNA methylation, “a chemical marker in DNA that can affect gene expression.” Both levels have since returned to normal.

He also saw slight decreases in cognitive ability and speed, though it’s unclear if the change is substantial enough to be related. It could take up to two years for scientists to release more detailed and thorough findings — something they will likely do through academic journals alongside news outlets.

But the reassuring part of this information seems to suggest for now that most changes to the body are short-lived and minor over a year’s time — the approximate length of time estimated to take a group of astronauts to reach Mars.

Maybe Hollywood’s wrong, and that interplanetary road trip isn’t going to be such a bummer.