NASA's only identical twin astronauts are planning to serve as guinea pigs for studies investigating the genetic impacts of long-duration spaceflight.
Astronaut Mark Kelly, who commanded four space shuttle missions including the final flight of Endeavour, is set to be a test subject on Earth while his twin undergoes studies in orbit.
Mr Kelly left NASA in 2011 to care for his wife, former US Representative Gabrielle Giffords, who was shot through the head in when a gunman opened fire at a political event in Arizona in January that year, killing six people.
His brother, Scott Kelly, is preparing for a year-long mission aboard the International Space Station, the longest single spaceflight NASA has ever attempted, Reuters reports. Four Russian cosmonauts lived for a year or longer aboard the now-defunct Mir space station.
The US space agency is soliciting ideas from researchers about possible experiments. Scientists would be looking for genetic differences in the twins due to one brother living in the gravity-free environment of space and the other on Earth.
Scott Kelly is a veteran of two shuttle missions and previously served as a space station crew member and commander. He will be paired with Russian cosmonaut Mikhail Kornienko for the year-long spaceflight and is set to board the station in March 2015, about a month after he and his brother turn 50.