PHOENIX — With the possibility of a Mars mission inching closer and closer to reality, astronaut Mark Kelly is doing his part to keep astronauts healthy.

But he isn’t doing it alone.

Kelly, 50, has an identical twin brother named Scott. Together, they will undergo a unique NASA study that will focus on “the effects of long-term space missions on the human body,” according to TODAY.com. The sub-focus is this: A “what if?” Mars mission.

In 2015, Scott will travel with a Russian cosmonaut and spend a year on the International Space Station, while Mark will stay in Arizona with wife Gabrielle Giffords, a former U.S. House representative.

Blood, saliva, cheek swab, and stool samples will be taken from both brothers at the same times before, during and after the one-year mission to study the effects of long space missions on the human body. Psychological and physical performance tests will also be conducted.

Scott Kelly said a mission to and from Mars could take three years, so participating in this joint study could have immeasurable, positive effects for astronauts on future missions.

Mark Kelly retired from NASA in 2011, after Giffords was shot in the head outside a Tucson grocery store.

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