In a first-of-its-kind experiment, NASA spent nearly one year monitoring the biometrics of identical twin brothers Scott and Mark Kelly.
The key difference: Scott lived on the International Space Station and Mark lived on Earth.
Scott’s 340-day stint in space marked the longest consecutive off-world trip by a human astronaut. He retired shortly after the conclusion of his trip in 2016.
“I was surprised at how long a year is,” said Scott. “It’s a really, really long time.”
During the journey, Scott and Mark participated in a number of biomedical studies, provided blood and urine samples, and received vaccines. By comparing the results, researchers were able to better understand the effects of long-term spaceflight on the human body.
According to a NASA press release, researchers observed “thousands and thousands of changes at the molecular and genetic level” including:
- Changes in gene expression and immune system response
- Changes in how DNA is packaged
- Changes in gut microbiome
- Temporary increase in height
- Better performance on cognitive tests
- Thickening of the retina
“The Twins Study provides the first integrated bimolecular view into how the human body responds to the spaceflight environment and serves as a genomic stepping stone to better understand how to maintain crew health during human expeditions to the Moon and Mars,” wrote NASA.
Perhaps the most crucial discovery was the success of the flu vaccine in space. Scott’s immune system responded to the vaccine in exactly the same way Mark’s immune system responded.
“A fully functioning immune system during long-duration space missions is critical to protecting astronaut health from opportunistic microbes in the spacecraft environment,” explained NASA.
Flu vaccines and other preventative measures will be necessary during NASA’s planned expedition to Mars by 2035. The roundtrip journey to the Red Planet is expected to take up to 913 days.
Another key discovery was the effect of spaceflight on Scott’s telomeres (the protective ends of chromosomes that shorten with age). Scott’s telomeres grew longer in space and then shortened back to normal averages when he returned to Earth.
All other changes Scott experienced in space appear to have reversed when he returned; but as noted in NASA’s official report, an estimated seven percent of the changes in Scott’s genes persisted for six months after he arrived on Earth.
More than anything else, the Twins Study will serve as a baseline that will influence all future astronaut studies.
“The vision of the future would be to look at the entire genetic code, all the molecular structures and changes in an individual, and then customize what he or she will need for long-term missions,” explains NASA. This could include changes to exercise habits, vitamins, and microbiome management.
The Twins Study encompassed 10 investigations conducted by 84 researchers at 12 locations. The results were published April 12th, 2019 in the journal Science.