His brother Mark Kelly is himself a former NASA astronaut of some repute, but he retired in 2011. "It turns out that big changes in the expression of Scott Kelly's genes occurred while he was in space, and 7 percent of those changes persisted after he returned to Earth, lead author Susan Bailey, a researcher at Colorado State University, who led the research on Kelly, told Nat Geo's Nadia Drake", Live Science's correction explained. "What researchers did observe are changes in gene expression, which is how your body reacts to your environment".
NASA's preliminary results expose that astronaut Scott Kelly's genetic expression did not return to baseline after his arrival to Earth.
Other than his DNA, the study found most of the biological changes Scott Kelly experienced in space returned to normal after just hours or days on Earth, although some took months. My DNA changed by 7 per cent?
"Whole-genome sequencing showed each twin has hundreds of unique mutations in their genome, more than expected, and some were found only after spaceflight, circulating in the blood as 'cell-free DNA, '" NASA said in a statement. What's important is which changes space seems to have made on Scott Kelly's body. What changed was the transcription and translation of some of S. Kelly's genes.
"We really see an explosion, like fireworks taking off, as soon as the human body gets into space", said Dr Chris Mason, Twins Study investigator, of Weill Cornell Medicine.
About 93 per cent of the changes reverted to preflight levels within six months of Scott's return to Earth.
The truth is, identical twins don't necessarily have identical DNA, even if that may sound hard to believe.
The altered genes are related to Scott Kelly's immune system, DNA fix and bone formation networks, among other bodily functions.
By measuring large numbers of metabolites, cytokines and proteins in Scott's body the team learnt that spaceflight is associated with oxygen deprivation stress, increased inflammation and dramatic nutrient shifts that affect gene expression.
Scientists also discovered that Scott's telomeres - the caps at the end of chromosomes that shorten with age - stretched in space, suggesting a possible protection against ageing.
The Twins Study has benefited NASA by providing the first application of genomics to evaluate potential risks to the human body in space. NASA considers this analysis a high priority because of the eventual plan to send astronauts to Mars for up to 3 years. They returned to normal within two days of landing back on Earth.