His twin brother, a retired astronaut, Mark Kelly back on earth.
In its report, Business Insider claimed that "seven percent of Scott Kelly's genes may have permanently changed". A twin study has now discovered that spending 1 year in space causes considerable changes in an astronaut's genes, altering DNA by almost 7 percent.
The Twins Study Investigators came from around the country to meet and share their final research results at the annual Human Research Program Investigators' Workshop held in Galveston, Texas. Overall, the 2018 findings corroborated those from 2017, with some additions. Scott's metabolites, which are necessary for maintaining life, cytokines, which are secreted by immune system cells, and proteins, which are the engines within each cell, all changed.
One finding - that his gene expression levels changed by 7percent - triggered a media sensation, with headlines about him "losing" part of his DNA.
The space agency recently released a preliminary analysis of the twin experiment, and one section of the post sent these outlets over the edge.
What changed in Scott was the way his DNA was transcribed and translated into functional products; the study of such shifts is called epigenetics. Whole-genome sequencing revealed that each twin has more than expected unique mutations in his genome - in fact, hundreds.
A percentage of Scott's genetic expression that underwent change did not revert back to baseline after his return to the Earth's surface more than two years ago. Gene expression did change by 7%, though. Also, problems such as abnormality elevated Carbon dioxide levels and hypoxia - a deprivation of oxygen supply at the tissue level - have wreaked a bit of havoc on Scott's body. While some private space firms are looking to take people to the red planet very soon, it's clear there's still a great deal we don't understand about the effects of space travel on humans. These epigenetic changes were likely the body's way of responding to the low gravity, oxygen deprivation, increased inflammation and diet challenges of space flight.
What really happened is that seven per cent of the way Kelly's DNA is expressed changed after space travel, as Daniela Bezdan, research director of the Mason Laboratory of Integrative Genomics at Weill Cornell Medicine, explained in a tweet and confirmed in an email to Gizmodo.
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. The remaining 7% are of particular interest because the changes persisted for longer durations of time.