The NASA Twin Study investigated the effects of long-duration spaceflight on the human body by comparing identical twin astronauts Scott and Mark Kelly. This research provided insights into the physiological, molecular, and cognitive changes experienced during extended periods in space. The study helps understand human adaptation to the space environment, aiding future long-duration missions.
The Unique Value of Twins in Space Research
Identical twins, like Scott and Mark Kelly, share nearly identical genetic material, making them valuable for scientific research. This genetic similarity allows scientists to minimize the influence of genetic variations when studying how different environments affect the human body. By having one twin in space and the other on Earth, researchers can attribute observed changes to the space environment rather than genetic predispositions.
Mark Kelly, remaining on Earth, served as the “control” subject, providing a baseline for comparison. Scott Kelly, as the “experimental” subject in space, experienced microgravity, radiation exposure, and isolation. This design enabled researchers to isolate the effects of space travel from inherent genetic differences, providing a clearer picture of how the human body responds to extraterrestrial environments.
Designing the NASA Twin Study
The NASA Twin Study involved ten research teams. The study spanned 25 months, collecting data before, during, and after Scott Kelly’s year-long mission aboard the International Space Station (ISS) from March 2015 to March 2016. Mark Kelly participated concurrently on Earth, undergoing the same tests and sample collections.
Researchers collected biological samples from both twins, including blood, urine, and stool. They also performed tests to assess physiological, molecular, and cognitive parameters. These included analyses of:
Gene expression
Immune system responses
Changes in telomere length
Gut microbiome composition
Fluid shifts
Vision alterations
Cognitive performance
Key Discoveries from the Study
The NASA Twin Study revealed findings regarding the human body’s response to long-duration spaceflight. Gene expression altered, with thousands of Scott Kelly’s genes changing activity levels in space. Many changes linked to stress responses, inflammation, and immune system function.
Scott’s telomeres, the protective caps at the ends of chromosomes, lengthened during his spaceflight, which typically shorten with age. Upon his return to Earth, most telomeres shortened and returned to pre-flight lengths within hours or days. The study found Scott’s immune system responded normally to a flu vaccine administered in space, similar to Mark’s response on Earth, indicating continued functionality.
Scott’s gut microbiome, the community of bacteria in his digestive system, showed shifts in composition during flight compared to pre-flight. Most observed changes in Scott’s body, including gene expression and microbiome composition, returned to near pre-flight levels within six months of his return to Earth. A small percentage of gene expression changes persisted. Some changes, like certain indicators of inflammation and immune response, were affected only after landing, possibly due to re-adapting to Earth’s gravity.
Implications for Human Spaceflight
The NASA Twin Study findings have implications for planning future long-duration human space missions. The study demonstrated the human body’s ability to adapt to the space environment, with many changes being transient. This data informs strategies for maintaining astronaut health and safety on extended missions, which could last for several years.
The research contributes to developing countermeasures for physiological and psychological challenges associated with prolonged space travel, such as microgravity, radiation exposure, and isolation. Identifying specific genes and biomarkers that respond to spaceflight can help in personalized medicine for astronauts, allowing tailored interventions to mitigate health risks. These insights aid safer and more successful human exploration of deep space.