RENEE MONTAGNE, HOST:
Later today, NASA is sending an American astronaut to live on the International Space Station for a full year. Only Russian cosmonauts have ever gone on such a long trip. NPR's Nell Greenfieldboyce reports this mission offers a unique opportunity for scientists because this astronaut has a twin.
NELL GREENFIELDBOYCE, BYLINE: In a NASA video, astronaut Scott Kelly recalls a meeting that occurred after he was selected to do the year in space mission. Officials were prepping him for an upcoming press conference.
SCOTT KELLY: And I asked the question, hey, if someone just asks will there be any comparative studies between you and your brother, you know, how should I answer that?
GREENFIELDBOYCE: His brother, Mark, is a retired astronaut and his identical twin. Now, apparently no one at NASA was planning to compare an earthbound twin with a twin on a long-duration space flight. But Kelly says a few weeks later, a program scientist came back to him.
KELLY: And said, you know, we took your question and we were kind of discussing it. And it actually looks like this might be something that the science community is interested in.
GREENFIELDBOYCE: Over the next year, researchers will scrutinize Scott and Mark Kelly, looking at space travel's effect on everything from gut bacteria to eyesight. Christopher Mason is a geneticist at Weill Cornell Medical College. He'll be searching for changes in gene activity.
CHRISTOPHER MASON: The advantage of this study is that we'll get a complete profile - I would even argue the most comprehensive molecular profile of a human being that's maybe ever been generated. And then, to boot, we'll get the comparison of someone on Earth who's an identical twin.
GREENFIELDBOYCE: His colleague Francine Garrett-Bakelman has already been collecting blood from the twins. She'll periodically get more samples that are returned to Earth. She says from just one set of twins, you can't draw any definitive conclusions.
FRANCINE GARRETT-BAKELMAN: But you can get some idea of what things might change over time between the space and earth.
GREENFIELDBOYCE: And that's something NASA needs to know as it contemplates longer spaceflights to places like Mars. This will be Scott Kelly's fourth space trip. He lived on the station once before for about five months and sent back a video tour of his cramped crew quarters. He seemed pretty comfortable.
(SOUNDBITE OF VIDEO)
KELLY: I sleep much better up here than I do in my own bed at home.
GREENFIELDBOYCE: But recently, he said that during his year in space, there are some things on earth he'll miss, like his children's birthdays, good food and the rain. Nell Greenfieldboyce, NPR News.
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