New Delhi: When retired astronaut Scott Kelly returned to Earth in March 2016, NASA carried out its Twin Study on him and his twin brother Mark Kelly.
The researchers began combining the data and reviewing the enormous amount of information looking for correlations, especially to gain insight into the changes space travel has or can have on the human body.
While the study's preliminary results revealed massive changes in their gene expression caused by space travel, more research has now shown that a year in space has caused a long-term change in Scott Kelly's DNA.
As per the study, seven percent of astronaut Scott Kelly's genes linked to the immune system, DNA repair, and bone formation, showed an unexpected change.
As part of the study, Scott spent a year in space while Mark, his identical twin, stayed on Earth as a control subject to look at the effects of space travel on the human body.
The findings showed that after returning to Earth, Scott started the process of readapting to Earth's gravity. Most of the biological changes he experienced in space quickly returned to nearly his pre-flight status.
While 93 percent of Scott's genes returned to normal after landing, seven percent remained unchanged.
This remaining seven percent points to the possible longer-term changes in genes related to his immune system, DNA repair, bone formation networks, hypoxia and hypercapnia, the US space agency said in a statement.
By measuring large numbers of metabolites, cytokines, and proteins in Scott's body the team learned that spaceflight is associated with oxygen deprivation stress, increased inflammation and dramatic nutrient shifts that affect gene expression.
Previous studies showed the effect on the body after the standard-duration six-month missions aboard the International Space Station (ISS).
But the "Twin Study" discovered what happens to the human body after spending one year in space, in a stepping stone to the impending three-year mission to the Mars.
The results were presented at the annual Human Research Program Investigators' Workshop held in Texas.
Further, a majority of Scott's telomeres – endcaps of chromosomes that shorten as one ages – which had become significantly longer in space, shortened within two days of his return to Earth.
The one-year resulted in no significant decreases in Scott's cognitive performance.
However, a more pronounced decrease in speed and accuracy was reported postflight, possibly due to re-exposure and adjustment to Earth's gravity, and the busy schedule that enveloped Scott after his mission, the agency said.
(With IANS inputs)