NASA sent one of the twin brothers into space, and he returned an alien

When astronaut Scott Kelly returned to Earth after a year spent in space, he became five centimeters taller. And these are not all the changes that scientists have recorded after Scott spent 340 days on the ISS.

Kelly became a participant in a study that NASA is conducting to find out how the human body changes after being in space. Twin brothers Scott and Mark Kelly were used as "test subjects". While Scott spent 340 days aboard the International Space Station, Mark stayed on Earth, giving NASA the opportunity to compare two identical sets of DNA.

The increase in growth is one of the few changes that scientists have recorded. After Scott returned to Earth, NASA conducted tests comparing the twins' DNA and found that Mark and Scott were now genetically different.

Researchers knew before that that space flights have an impact on the human body — for example, they stretch the spine, change the sleep cycle — but the consequences of prolonged exposure have been less studied.

The results of gemini studies give scientists a lot of reasons to think. Christopher Mason, the head of the study and an associate professor at Weill Cornell Medicine College, said that scientists have seen "thousands and thousands of genes change the way they turn on and off" as soon as an astronaut is in space. Some of these changes persist for days or even weeks after returning to Earth.

Scientists are still studying how much being in space changed Scott's DNA. The researchers hope to use the full data set, which may take some time, to better prepare for future long-distance flights.