NASA Twin Astronauts Become Space Guinea Pigs

Expedition 26 Commander Scott Kelly (left), is reunited with twin brother, Mark Kelly on March 17, 2011, following a flight to Ellington Field in Houston from Kustanay, Kazakhstan after 159 days in space, 157 days on the International Space Station. (Credit:  NASA)
Expedition 26 Commander Scott Kelly (left), is reunited with twin brother, Mark Kelly on March 17, 2011, following a flight to Ellington Field in Houston from Kustanay, Kazakhstan after 159 days in space, 157 days on the International Space Station. (Credit:

By Laura Niles
International Space Station Program Science Office
NASA’s Johnson Space Center

“Twin minds think alike” is not a common phrase in the public dialogue, but in the case of twin astronauts, it may someday become one. In a spark of astronaut, and possibly familial, curiosity, twin NASA astronauts Scott and Mark Kelly initiated an unprecedented research request to study the human effects of spaceflight using their identical twin genetic makeup. NASA’s Human Research Program (HRP) realized that another opportunity to study astronaut twins would be rare, and took the brothers up on their offer of genetic comparison in the name of human space exploration.

HRP and the National Space Biomedical Research Institute opened the Human Exploration Research Opportunities Program asking potential researchers to propose cleverly designed, but limited, short-term investigations for observational comparison between astronaut Scott Kelly and his identical twin brother, retired astronaut Mark Kelly. These pilot demonstration projects, the first of their kind, will be unique investigations into the genetic aspects of spaceflight. They will provide insight into future genetic investigations that can build on this study, but with a larger study population of unrelated astronauts.

“This is a once-in-a-space-program opportunity,” admits John Charles, Ph.D., chief of the HRP’s International Science Office. “The mission of the HRP is to reduce the risk to astronauts during long-duration space flight. In typical investigations, we usually have a specific outcome in mind and are goal-oriented. In this case, the slate is essentially blank. I am anxious to see what proposals we receive from the scientific community.”

The selected investigations will occur during astronaut Scott Kelly’s yearlong spaceflight, the longest space mission ever assigned to a NASA astronaut, aboard the International Space Station beginning March 2015. Retired astronaut Mark Kelly will live out his normal life on Earth during Scott’s one-year mission. Scott, a veteran of two space shuttle flights and a six-month space station mission, will have a cumulative duration of 540 days in low-Earth orbit at the end of his one-year mission aboard the orbiting outpost. Mark, a veteran of four space shuttle flights, has a cumulative duration of 54 days in low-Earth orbit.

Since Mark will not be a typical research control subject, meaning his environment and living habits will not mimic those of Scott’s on the space station, the research is considered observational in nature. There are no defined outcomes for the investigations; instead, this is a chance to compare data collected from genetically similar astronauts to observe the human effects of spaceflight.

Tentative plans for data collection on the twins currently include blood sampling on Scott at regular intervals before, during and after the one-year mission on the space station and corresponding blood sampling on Mark, who will otherwise be living his normal lifestyle in Arizona. Limited additional samples, such as saliva, cheek swabs, stool or additional blood, or psychological or physical tests will be considered only for study if they do not interfere with the primary investigations aboard the space station and will help identify one or more aspects of brief or long-term effects of spaceflight on humans.

Proposed investigations should focus on the analysis of human molecular responses to the physical, physiological and environmental stressors associated with human spaceflight. Investigations should include multiple methods of study. One example would be the effects of the space environment on human DNA. Another may include changes in the small molecules in the blood, saliva, urine or stool as they are affected by astronaut diet, stress, weightlessness and other unique responses to spaceflight. Other methods of study for the twin comparison investigations are identified in the research announcement.

“The genetic revolution has reached space science and the space age,” asserts Charles. “This is an opportunity to explore and see what’s out there. We are prepared for any kind of suggestions that the scientific community presents that are peer-reviewed.”

A multitude of human research investigations currently are underway and are scheduled for upcoming expeditions aboard the space station by NASA and its international partners. The opportunity to compare the effects of spaceflight accumulated over one year and observe changes in the genetic makeup between twin brothers is new. These investigations could have lasting implications for protecting astronauts on deep space exploration missions, including travel to asteroids and Mars.

The data gathered from these investigations may also inform future human health studies on Earth by adding to current knowledge and practices in genetic research. Some investigations may study the impact of exposure to stress, radiation and life in a confined environment on the chemical compounds that tell a human cell what to do and when to do it. This information would be applicable to similar human exposures on Earth and may introduce new ways of thinking about genetic processes based on any genetic differences observed between the Kelly twins after the one-year mission.

Proposals for the NASA solicitation, “Differential Effects on Homozygous Twin Astronauts Associated with Differences in Exposure to Spaceflight Factors,” are due Sept 17. The estimated selection announcement for the chosen investigations will be January 2014.

Having this rare opportunity to study twin astronauts is expected to contribute significantly to HRP’s goals of risk reduction for human space exploration and also help identify new avenues for human health investigations in spaceflight. The Kelly twins will help NASA gain a deeper understanding of the fundamental changes in the human body during spaceflight. In the case of genetic investigations when it comes to spaceflight, two is definitely better than one.