NASA astronaut Scott Kelly spent a year in space and came back a slightly changed man – at least, in comparison to his twin brother Mark, who was earthbound while Scott was aboard the International Space Station. This experiment, conducted from March 2015 to March 2016, will help us plan for astronauts to travel for years to Mars or beyond.
Scott and Mark (himself a former astronaut) both gave NASA scientists samples of their blood, urine and faeces before, during and after the year-long flight – Scott’s samples were ferried back to Earth in Soyuz capsules returning other astronauts from the ISS.
Scott’s DNA saw some changes, compared to his twin. His telomeres – the endcaps of chromosomes that usually shorten as we age – lengthened over the 340 days he spent in space. This could be due to exposure to space radiation, according to the NASA team that released these results. Within 2 days of returning to Earth, his telomeres rapidly shortened and returned to their pre-flight length within months.
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One big difference between the twins was seen in their urine. Their metabolites – the products of metabolic processes – were similar in their blood plasma, but 32 urinary metabolites were significantly altered during spaceflight.
On the other hand, their faecal samples retained similar microbial communities – both dominated by bacteria from the Firmicutes and Bacteroidetes phyla. Mark’s faecal microbiome varied more than Scott’s from pre- to post-flight, but the changes were not significant.
NASA also found that Scott’s immune system responded similarly to Mark’s when given a flu vaccine, suggesting that immunisations in space should work as we expect, if they are needed in the future.
We’re only just beginning to understand the long-term effects of living in low gravity and exposure to space radiation, and while this study helps further our knowledge, it’s based on just one astronaut.
“The twins study demonstrated on the molecular level the resilience and robustness of how one human body adapted to the spaceflight environment,” said Jenn Fogarty, chief scientist at NASA’s human research program, in a statement. “This study was a stepping stone to future biological space research focusing on molecular changes and how they may predict health and performance of astronauts.”
Science
