Mark Kelly, right, and Scott Kelly will work together, though only Scott will be in space. (Associated Press)

Astronaut Scott Kelly is gearing up for a one-year stint on the international space station next spring. And his twin brother will be offering more than moral support.

That brother, retired astronaut Mark Kelly, will undergo medical testing before, during and after Scott Kelly’s flight.

In an unprecedented study of identical twins, researchers hope to better understand how prolonged weightlessness affects the body. They will do so by comparing the space twin with the ground twin.

Scott Kelly, 50 years old, has volunteered to spend a year on the space station beginning in March. He’ll work beside Russian cosmonaut Mikhail Kornienko (pronounced “korn-YEN-koh”).

The earthbound Kelly draws the line, though, at eating space station food.

“It’s not bad when you’re in space,” said Mark Kelly, who orbited Earth on the space station hundreds of times between 2001 and 2011. But he won’t open up “a can of Russian lamb and potatoes when I’m out to eat with my friends.”

— Associated Press