UPDATE: This story is incorrect. The corrected version is here.

LiveScience:

Scott and Mark Kelly are identical twin brothers — at least, they were until Scott spent a year living in space.

When Scott Kelly returned to Earth after a 340-day voyage aboard the International Space Station (ISS) two years ago, he was 2 inches taller than he’d been when he left. His body mass had decreased, his gut bacteria were completely different, and — according to preliminary findings from NASA researchers — his genetic code had changed significantly.

While most of these genetic changes reverted to normal following Scott Kelly’s return to Earth, about 7 percent of the astronaut’s genetic code remained altered — and it may stay that way permanently.

This is all kinds of mind-blowing and may have real consequences as we go forward into space. Thaks to my friend Mike Rose for the link.