After spending an exhausting nine months in space, it’s no surprise that the NASA astronauts who were ‘stuck’ in orbit have undergone some noticeable changes.

On Tuesday (March 18), astronauts Barry ‘Butch’ Wilmore and Sunita ‘Suni’ Williams finally returned to Earth aboard the SpaceX Dragon spacecraft after being ‘stranded’ on the International Space Station (ISS) since June of last year.

Spending such a long time away from Earth inevitably takes a toll on the body, something NASA is well aware of. This was evident when the crew was immediately placed on stretchers upon landing in the Gulf Coast near Tallahassee, Florida—before they even had a chance to stand on solid ground.

Aside from finally breathing fresh air again, Wilmore and Williams are also experiencing the pull of gravity on their bodies for the first time in nine months—something that brings its own set of health concerns.

According to the Daily Mail, potential issues range from weakened muscles and sensitive feet to a heightened risk of cancer, meaning the astronauts aren’t entirely in the clear just yet.

As they undergo a series of medical tests at NASA’s Johnson Space Center in Houston, some experts have already pointed out early signs of possible health deterioration.

Observers have noted that before-and-after photos of Wilmore and Williams suggest they may have lost weight in space, with both appearing noticeably thinner.

Beneath the surface, experts suggest that fluid buildup in the head—caused by pressure on the eyes and optic nerves—could be altering their appearance.