Mark and Scott Kelly are identical twins who were both selected for NASA's astronaut program. They are the only siblings ever to both fly in space. Mark Kelly flew the space shuttle for ten years, then retired in order to take care of his wife. Scott Kelly spent an entire year in space aboard the ISS. Now NASA is studying the differences between the two after Scott's year in space, and the early results are intriguing.
As identical twins, the brothers are genetically very similar. However, researchers found that while he was in orbit, Scott’s telomeres—the caps on the ends of chromosomes—grew longer than his twin brother’s. Though Scott’s telomeres returned to their pre-flight lengths shortly after he returned to Earth, these results were totally unexpected, since telomeres naturally shrink over the course of one’s life, and the stresses of spaceflight are supposed to accelerate this. At least that was the idea.
“That is exactly the opposite of what we thought,” Susan Bailey, a radiation biologist at Colorado State University, told Nature.
That's not the only genetic difference they found in the twins. Read more about the study at Gizmodo.
(Image credit: NASA)