NASA said Thursday that astronaut Scott Kelly had grown nearly five centimeters (1.5 inches) after spending nearly a year aboard the International Space Station (ISS).
Researchers at the space agency pointed out that the growth is due to the lack of gravity in outer space, which causes the spinal disks to expand.
Kelly descended to Earth on Tuesday, landing in the Kazakhstan desert in a capsule with two Russian cosmonauts.
By the time the twins were reunited on Wednesday, the 1.5 inch (3.8 cm) increase in height Kelly experienced as a result of his spine expanding in microgravity had reversed.