Out-of-this-world experiment
A 25-month study of twin astronauts Scott and Mark Kelly has shown that lengthy space missions do not cause substantial changes in a human’s physiology.
Results of the study were published Thursday in the journal Science, almost exactly four years after Scott Kelly in March 2015 embarked on a 340-day stay on the International Space Station.
Kelly was the first person to live on the space station for 11 months, undergoing numerous tests as NASA tracked his vital signs and body changes. Simultaneously, NASA was conducting the same tests on Mark Kelly for comparison.
Knowing how a person’s body reacts to long-term space flight is vital if NASA wants to move forward with deep space exploration — especially now that Vice President Mike Pence has directed the space agency to put humans on the moon by 2024, four years earlier than originally planned.
“The valuable data gathered from the twins study has helped inform the need for personalized medicine and its role in keeping astronauts healthy during deep space exploration, as NASA goes forward to the moon and journeys onward to Mars,” said J.D. Polk, chief health and medical officer at NASA headquarters in Washington, D.C.
More than 80 researchers from 12 universities worked on this study, tracking the brothers before, during and after flight. Scott Kelly experienced many changes to his body, both inside and out, but most functions returned to normal when he came back to Earth. Scientists concluded that Kelly’s time in space didn’t cause substantial or lasting changes.
The most significant finding released Thursday is that Kelly experienced changes in his telomeres, or the ends of his DNA strands. Telomeres protect chromosomes — without them, cells don’t work properly — and typically shorten as humans age.
But during Kelly’s year-long mission, his telomeres actually lengthened. Once he returned to Earth, the telomeres shortened rapidly — within 48 hours — and returned to mostly normal within the following months, according to the study.
“We had a question about aging and whether or not Scott would come back younger,” said Susan Bailey, principal investigator for the telomeres study from Colorado State University. “We couldn’t have been more surprised by what we saw.”
Bailey said researchers are not sure why this happened, though she hypothesized it could be related to radiation exposure while in flight.
Other changes that occurred during Scott Kelly’s year in space included thickening of his carotid artery, retinas and the skin on his forehead (because of how body fluid shifts in zero gravity) as well as changes in his genes.
The study also determined that Kelly’s immune system responded the same way in space as it does on Earth, meaning vaccines could be administered safely during deep space missions. This was tested by giving him a flu shot in space; the vaccine worked as it would on earth.
Earlier phases of the study showed that Kelly’s genes — related to a person’s immune system and DNA repair, for example — also changed temporarily.
Scientists found that 93 percent of Kelly’s genes returned to normal after he returned to Earth. But 7 percent experienced longerterm changes, according to a Jan. 31, 2018 post on NASA’s website.
Additionally, NASA researchers found that Kelly’s increased time in space did not significantly decrease his cognitive performance on the space station when compared to that of his twin on the ground.
Kelly’s mission also helped scientists learn that spaceflight is associated with increased inflammation and oxygen deprivation, among other things, according to NASA.
Scientists on Thursday cautioned that these results were just one data set, specific to the two brothers. Much more investigation must be done before applying the results to all deep space explorers.