Story highlights Scott Kelly grew taller during his 340 days in space

After about 28 hours, he was back to normal height

Since his return to Earth, the astronaut has shared photos of life on the ground

(CNN) Well, that didn't last long.

Astronaut Scott Kelly, who grew about 2 inches during his nearly one year stay on the International Space Station, is back to his normal height, his identical twin brother, Mark, said Thursday.

Scott Kelly, whose spine elongated while he spent 340 days in space, took less than two days to shrink.

Mark Kelly, a former astronaut, told CNN's "Erin Burnett OutFront" by email that the two went back-to-back an hour after his brother returned to the United States early Thursday.

Scott grew 1½ inches before returning to normal, he said.