Washington – The retired Kelly twins astronauts, Scott and Mark, of age 51 are the first twins to participate in an experiment by NASA to evaluate the long-term effects of space radiation and microgravity on the human body and mind.

Mark currently stays at his Arizona home, where every few weeks he takes a memory and judgement online test. Meanwhile, his identical brother Scott remains 200 miles above earth where he takes the same online test only at the International Space Station. Up there Scott isn’t logging science reports, he is photographing the world at the International Space Station orbits earth.

Astronaut twins Mark and Scott Kelly. Credit: NASA

On Tuesday, 342 days will have passed since Scott, and housemate Russian cosmonaut Mikhail Kornienk started orbiting the earth for living. When they come back they will have spent more time in space than any other U.S. astronaut. The focus of their mission is for scientists to analyze their data and determine how to prepare astronauts for a round trip to Mars that could take as long as three years.

In addition to taking cognitive tests, the Kelly twins regularly provide samples of blood, saliva and other bodily fluids. And they undergo MRIs and ultrasound tests so researchers can study what protracted time in space does to bone density, cell tissue and other DNA markers.

The brothers are the first ever twins to travel to space. They not only provided NASA with the opportunity to test on genetically identical individuals, but also they’ve had similar careers, both were Navy pilots who became astronauts in 1996.

Source: NASA