Why Sunita Williams will grow shorter after return to Earth

After being stuck in space for nine months, Nasa astronauts Sunita Williams and Barry “Butch” Wilmore returned to Earth on Tuesday (March 18) in a SpaceX capsule. The Crew Dragon spacecraft had a splashdown off Florida’s coast, hours after it departed from the International Space Station (ISS).

Now that they are back on Earth, the duo will have to readjust to life with gravity. This means that the changes their bodies had experienced in space will reverse. Williams, Wilmore and the other two astronauts who returned in the SpaceX capsule will also grow shorter.

Here’s why.

Changes in astronauts’ bodies in space

From their DNA to vision, astronauts’ bodies change in a significant way during space travel. Microgravity is responsible for many of the changes that astronauts experience in space.

Without Earth’s gravity, they start to lose bone density and their muscles begin to diminish.

A stay in space could also affect their weight, immune and cardiovascular systems, vision and DNA.

Studies show that astronauts could also lose motor control, coordination and balance in space, which puts them at a higher risk of injury.

Astronauts also become taller in space, developing a “space height”. Bodily fluids shift during their stay in space, which could give them “chicken legs” and a “puffy head.”

Most of these changes reverse shortly after the astronauts return to Earth.

“There is some individual variability on how quickly they recover, but it is pretty impressive to see how they will turn the corner and really adapt quickly,” Dr Joe Dervay, one of Nasa’s flight surgeons, told CNN. “Oftentimes, if you look at them a couple days later, you really have no idea what they’ve just done for the last several months.”

Why astronauts get taller in space

Astronauts’ height in space can increase up to 3 per cent while living in microgravity, according to Nasa. For example, astronaut Kate Rubins went from 5’6” to a “space height” of 5’7.”

This happens as a person’s spine straightens when not exposed to the pull of Earth’s gravity, making them taller.

Williams has previously spoken about “space height”. In an old interview, the Nasa astronaut discussed the changes in the human body during space travel.

“Calluses on your feet disappear because you don’t walk, and fingernails and hair grow faster. Without gravity, some wrinkles on your face might go away due to a couple of reasons, one because there is a fluid shift. Your spine also expands because there’s no pressure on the cartilage between your vertebrae, making you slightly taller in space," she explained.

As per Nasa, astronauts get taller in space because of 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 slight increase in height makes astronauts vulnerable to back pain in space and slipped disks after their return to Earth.

Is ‘space height’ permanent?

No. Like most other changes in astronauts’ bodies in space, the increase in height also reverses when they are back on Earth.

Astronauts growing tall in space is short-term as their heights return to normal in a few months after their return to Earth, as per Space.com.

Williams and Wilmore’s bodies will also recover now that they have returned to Earth. They will be staying at Johnson Space Center in Houston for the coming days before the flight surgeons give them the go-ahead to return home.

“Almost every organ system in the body is impacted to some degree – whether it’s the skin, the neurovestibular, the bone, muscle, the immunological system, the cardiovascular system – so we have programs that our Human Health and Performance team focuses on to try and make sure that we’re covering all those areas,” Nasa’s Dervay told CNN.

With inputs from agencies