Research by NASA on identical twins has revealed that being in space changes human genes. So researchers tested both brothers before, during and after Scott's year in space to map specific changes in the astronauts' physical and mental health. But about 7% of the changes have remained in the two years since he returned to Earth.
They gathered the evidence after looking at "large numbers" of proteins (chains of amino acids), cytokines (substances secreted by cells in the immune system) and metabolites (substances related to metabolism) in Scott's body. They took these measurements before, during, and after the mission, and their results so far show that the stresses of spaceflight can fundamentally affect gene expression.
While extended space time altering human DNA is fascinating, it raises a big question: did Kelly's genes actually change because of space or because of the stress associated with space?
In this July 12, 2015 photo, Astronaut Scott Kelly takes a photo of himself inside the Cupola, a special module of the International Space Station which provides a 360-degree viewing of the Earth.
"Another interesting find concerned what some call the 'space gene, '" the Administration said.
After the return of Scott to the Ground only 93% of his DNA returned to normal.
Unlike Japanese astronaut Norishige Kanai, who claimed to have grown 9 cm (3.5 inches) during his trip to the cosmos, Kelly came home an impressive 2 inches taller than his twin. My DNA changed by 7%! From the challenges of growing and providing nutritious foods to managing an environment fraught with risks from radiation, lunar dust, zero-gravity conditions, and more, the Human Research Program (HRP) was established as a result of NASA's refocus of the space program on exploration in early 2004.
Because of the change, Kelly and his brother-retired astronaut Mark Kelly-are no longer considered identical twins. To say for sure whether these changes were caused by his time in space, scientists would have to study Scott's DNA for a longer period of time.
Last year, NASA published its first round of preliminary results at the 2017 Investigator's Workshop.
NASA clarifies in the report 93 percent of Scott Kelly's genes returned to normal after he came home, but that the missing 7 percent points "to possible longer-term changes in genes related to his immune system, DNA fix, bone formation networks, hypoxia, and hypercapnia".
Changes like the longer telomeres disappeared after 48 hours of being back on Earth.