Are identical twins still identical after one spends a year in space?
The question is not theoretical, as NASA prepares to return astronaut Scott Kelly to the International Space Station, this time for an unprecedented one-year stay, while his identical twin brother Mark, a former astronaut who flew four times on the space shuttle, serves as a test subject on the ground.
Scientists are curious if the 50-year-old twins, who share nearly identical DNA, will end up with detectable genetic differences after one spends a year in the highly radioactive and weightless environment of space.
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"Everybody is pretty much born with a set of genes that they don't have on the day they die. Your genes mutate for a number of different reasons, also because of the environment," Mark Kelly told Discovery News.
"The environment that Scott is going in is pretty unforgiving, a lot of radiation, no gravity and lots of opportunities for genetic material to change and for genes to mutate," Kelly said.
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So far, the longest single U.S. space mission lasted 215 days. Russia has four longer-duration fliers, including Valery Polyakov, who spent a record 438 days aboard the now-defunct Mir space station.
In March, Scott Kelly, along with cosmonaut Mikhail Kornienko, are due to begin a year-long stay aboard the space station, twice as long as current crewmembers' assignments. Unlike Mir, the space station is outfitted with very sophisticated medical equipment.
Doctors will be sequencing the genes of both Kelly brothers, then looking for different markers.
"Onboard the space station, it just looks like blood sampling but what you do when you get those samples home is brand new. We've never had data like that before," said station chief scientist Julie Robinson.