"Because they're identical twins, we might be able to see things we ordinarily might not be able to detect if we were just taking two people out of the population," Dr. Craig Kundrot, deputy chief scientist for NASA's Human Research Program, told Business Insider.
Moreover, Kundrot says, "This study is a special opportunity given the rarity of identical twin astronauts. "
In March 2015, astronaut Scott Kelly will begin a yearlong stay aboard the International Space Station, a duration longer than any person before him and double the standard duration. Scott's identical twin brother, astronaut Mark Kelly, will remain on Earth during that time, allowing scientists to closely compare their two bodies.
Scientists will conduct tests and measurements of both Kelly brothers before, during, and after the 2015 mission. Since twins are more genetically alike than any other pair of humans, Mark can serve as a control in this experiment by remaining on Earth.
"Our DNA is not all that different, but it's still different enough to make wildly different types of people," Kundrot said. "When you have identical twins, you've eliminated almost all of that difference."
As part of the study, the twins will both get flu vaccinations to help scientists learn more about how space changes the immune system. "We expect Mark on the ground to have a normal kind of response and we're really curious to see what happens with Scott in space," Kundrot said, "because the immune system has a number of changes to it and when challenged with a flu vaccine, the question is will it respond in a usual way or in a different way."
The study will help scientists figure out how to counteract stressors in space like radiation, weightlessness, confinement, and monotony.
"A lot of what we do in the Human Research Program is try and understand how to do things for the astronauts so they can be more Earth-like in function," Kundrot said. "We don't want them to be unable to perform they're tasks in space."
Despite the value of the Kelly brothers as identical twins, the study is limited because there are only two subjects for data collection. "In the case of Mark and Scott Kelly, the genetics are the same, so we are in a position to detect more subtle changes," Kundrot said. "If we do see some subtle changes or even dramatic changes, we have to remember that it's just these two individuals. We will regard that as a clue that needs to be followed up in a more thorough study."
NASA would be interested in conducting the study again on another pair of identical twins, Kundrot said. "But to my knowledge there are no plans to specifically try to recruit twins into the astronaut corps," he said.
This excerpt from a NASA press release explains four broad focuses of the study, which will be jointly managed by NASA and the National Space Biomedical Research Institute (NSBRI):
The studies will focus on four areas: human physiology, behavioral health, microbiology/microbiome, and molecular or -omics studies. Human physiological investigations will look at how the spaceflight environment may induce changes in different organs like the heart, muscles or brain within the body. Behavioral health investigations will help characterize the effects spaceflight may have on perception and reasoning, decision making and alertness. The microbiology/microbiome investigations will explore the brothers' dietary differences and stressors to find out how both affect the organisms in the twins' guts. Lastly, but potentially opening a whole new realm of information about humans exposed to the spaceflight environment are the molecular or -omics investigations. These studies 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.