Of all the members of NASA's current crop of distinguished astronauts, only two have the unique distinction of being identical twin brothers. And now NASA is using an idea proposed by the brothers, Mark Kelly and Scott Kelly, to perform a study that's been confined to sci-fi up until now. Beginning in March 2015, the space agency will be monitoring the biological states of both twin brothers over the span of a year, with a twist: Scott will be aboard the International Space Station for the duration of that period, while Mark, who retired from NASA back in 2011, will remain back here on Earth.

NASA announced the experiment last week in a request for research proposals, but sadly didn't specifically call out the "twin paradox," a 1911 thought experiment by French physicist Paul Langevin that says an astronaut in space should age slower than his twin on Earth due to relativity. The theory later served as the basis of Robert Heinlein's sci-fi novel Time for the Stars. But NASA doesn't seem to be interested in studying relativity for this particular expedition. Instead, it described the basics of how the experiment will work in its request document:

As currently conceived, this project will center on established plans for blood sampling on the flying twin at regular intervals before, during and after the one-year ISS mission, and will obtain corresponding samples from the non-flying twin, who will otherwise maintain his normal lifestyle.

NASA explained it will be looking for research proposals that focus on specific biological attributes in particular, including the effects of space on genetic mutations in Scott, protein levels in the two astronauts' bodies, the levels of other biological molecules, and differences in astronaut psychology between Earth and space. Incidentally, it should also be noted that Mark is also the husband of former Congresswoman Gabrielle Giffords (D-AZ), who was critically wounded in an assassination attempt in early 2011, but has since recovered. NASA has of course previously studied such differences in individual astronauts before, during and after space flights, but this will be the first study of its kind to examine two genetically identical individuals separated by space at the same time.

NASA said that it will be issuing up to 10 awards for research proposals to study the brothers, each worth up to $50,000, and the winners will be announced by January 2014. Researchers interested in submitting their experiment ideas for the astronauts have up until September 17 to do so. In the meantime, check out a revealing NASA interview with the Kelly brothers from 2010.