Twins separated by outer space are no longer identical.
As part of NASA’s Twins Study, astronaut Scott Kelly was sent to space, while his brother Mark, also an astronaut, stayed on Earth.
NASA created the study to research how one year in space could affect the human body.
Researchers took biological samples from Scott before, during and after his mission and then compared them to Mark’s samples.
Preliminary results revealed that 7 per cent of Scott’s genes did not return to normal after his return to Earth two years ago.
NASA has learned that the formerly identical twins are no longer genetically the same, with Scott’s chromosomes lengthening during his time in space.
He also returned to earth five centimetres taller.
Around the time Scott returned, NASA spokesman Jeff Williams told CNN astronauts got taller in space as the spine elongated.
“But they return to pre-flight height after a short time back on Earth,” he said.
Scott’s cognitive performance was also slightly affected during the one-year mission, with NASA measuring a decrease in speed and accuracy compared to his brother once he returned.
NASA said that may have been due to re-exposure to Earth’s gravity.
Researchers measured metabolites, cytokines and proteins and found changes in the body could have occurred due to oxygen deprivation stress, increased inflammation and dramatic nutrient shifts.
Scott travelled 230 million kilometres during his mission, chronicling his journey with regular updates and spectacular pictures on social media.
Back on Earth, Mark posted about facets of his daily life.
Study to identify risks for astronauts
In a press release, NASA said some of Scott’s bodily changes returned to normal within hours and days of landing.
However, some changes persisted for six months.
“Researchers now know that 93 per cent of Scott’s genes returned to normal after landing,” NASA said.
“However, the remaining 7 per cent point to possible longer-term changes in genes related to his immune system, DNA repair, bone formation networks, hypoxia, and hypercapnia.”
The study was created to identify any risks space travel may have for humans.
Mark and Scott were the only identical twin astronauts in history.