Astronaut Scott Kelly, the American who has spent the longest time at the International Space Station, or ISS, grew 2 inches (5 centimeters) taller in less than a year during his last mission, local media reported.
Kelly, who returned to Earth last Wednesday after successfully completing his space mission, found that his spine had stretched for lack of gravity.
On Earth, the power of gravitation compresses the bones, but in outer space, its absence allows the vertebrae to drift apart, the CNBC network said.
Nonetheless, after a few hours back on Earth, Kelly regained his original stature and was again exactly the same height as his twin brother Mark, a retired astronaut, the brothers told CNN.
The astronaut was in space for 340 days studying the physiological changes that being in space causes the human body.
The findings will be applied on future missions to explore the universe, particularly on possible expeditions to Mars, NASA Administrator Charles Borden and the director of the White House Office of Science and Technology Policy, John Holdren, said on Thursday.
Kelly, 52, is taking part together with his twin brother in 10 research projects dealing with human psychology, health, microbiology and molecular studies in which two sets of data are being compared, one from space and the other from Earth.