With all eyes on eventually sending human crews to Mars, NASA’s One-Year Mission provides a rare opportunity to conduct parallel studies on identical twin astronauts: “one twin flying and one twin on the ground,” Craig Kundrot, deputy chief scientist of NASA’s Human Research Program, explains in this NASA video.

As detailed by the Human Research Program, the investigations conducted on twin brothers Scott and Mark Kelly — Scott is flying a one-year mission on the International Space Station, and Mark is being observed on Earth — “will provide NASA with broader insight into the subtle effects and changes that may occur in spaceflight as compared to Earth-based environments.”

NASA’s Human Research Program, at www.nasa.gov/twins-study/reseach, details the four main research areas on which a total of 10 investigations on the identical twin brothers are being focused:

• Human physiology: These investigations will look at how the spaceflight environment may induce changes in different organs like the heart, muscles or brain.
• Behavioral health: This investigation will help characterize the effects spaceflight may have on perception and reasoning, decision making and alertness.
• Microbiology/Microbiome: This investigation will explore the brothers’ dietary differences and stressors to find out how both affect the organisms in the twins’ guts.
• Molecular/Omics: These investigations will look at the way genes in the cells are turned on and off as a result of spaceflight; and how stressors like radiation, confinement and microgravity prompt changes in the proteins and metabolites gathered in biological samples like blood, saliva, urine and stool.