Japanese astronaut Norishige Kanai tweeted that he's grown grown 9 centimeters (about 3.5 inches) since arriving on the International Space Station only three weeks ago.
"I grew like some plant in just three weeks," Kanai wrote. "Nothing like this since high school. I'm a bit worried whether I’ll fit in the Soyuz seat when I do go back."
Kanai is scheduled to be on the Space Station until June.
Astronauts do "grow" an average of 2 to 5 centimeters when they spend time in low gravity space environments as their spines expand, but Libby Jackson of the UK Space Agency told BBC News, “9 centimeters is a lot, but it is possible, knowing that every human body is different.”
“You do get taller in space as your spine drifts apart,” Jackson continued. “There’s a range of growth for different people, and everybody responds differently.”
Astronauts usually return to their previous height after returning to Earth as their spines recompress.
Recent NASA research has shown atrophy in the muscles supporting the spine after space travel, which can last weeks or months after returning to Earth, Sky News reported.
It is the first space mission for Kanai, who previously served as a diving medical officer with the Japan Maritime Self-Defense Force.
The Soyuz spacecraft that ferries astronauts to and from the Space Station does have a height limit and is built for specific height requirements. Crew members’ height could become a problem if they grow too tall, but it was not clear whether Kanai’s current height would actually be problematic, the BBC reported.
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