Why stranded NASA astronauts could have returned to Earth taller than they were before

Suni Williams and Butch Wilmore might find they're a bit taller after returning home from their longer-than-expected stint in space.

Williams and Wilmore have recently returned from the International Space Station after nearly 10 months up there.

The two NASA astronauts received a warm welcome home when they landed off the Gulf Coast on Tuesday (March 18) and were greeted by a pod of dolphins.

Quite the homecoming, or what?

I'm sure the pair are extremely relieved to finally be back on Earth, but their mission isn't quite over yet as they'll need to endure 45 days of rehab after their ISS stay.

Apparently most astronauts will recover within this time frame but Williams and Wilmore's rehab will be extended if need be.

They'll be noticing some changes to their bodies since returning to Earth, one example being to their immune systems.

READ MORE: Six physical health issues NASA astronauts face after nine months stranded on the International Space Station as they return to Earth

Now they're home, the duo may find that their skin is more irritable as a result of their lowered immune systems.

But there's something else the now-very famous astronauts might notice, and that is that they're taller than before.

Butch Wilmore and Suni Williams jetted off to the ISS last year (Joe Raedle/Getty Images)

On Earth, humans typically stop growing around the age of 18, but astronauts could find that they're a couple of inches taller post-space mission.

This happened to Scott Kelly. He found that when he returned from the ISS, he was two inches taller than his twin brother, Mark.

Scott spent the best part of a year up in space.

Why do astronauts grow in space?

NASA has conducted studies into astronauts growing while in space and found that their height 'increases approximately three percent over the first three to four days of weightlessness in space'.

Astronaut Scott Kelly grew two inches after spending almost a year in space (Eduardo Parra/Getty Images)

The agency goes on to explain: "In space, almost all of this height increase comes from changes in the spinal column, which affects body measurements such as sitting height, eye height, standing height, how space suits fit, and much more."

The amount someone grows depends on each individual.

Will astronauts stay that height?

For anyone who might want to be a bit taller, it's bad news as NASA says that when astronauts are back on Earth, it's likely they'll return to their original height.

"As soon as astronauts return back to Earth, gravity pulls on them once again and astronauts will typically return to their pre-flight height in a short amount of time," it said.

With Scott having landed back on Earth from the ISS back in 2016, it's highly likely he's now the same height as his twin brother again.

Williams and Wilmore, however, might still be experiencing their new — but temporary — height, having only been back on their home soil for a couple of days.