Scott Kelly, a NASA astronaut, grew 2 inches after a year in space

Kelly, who has spent more time in space than any other American astronaut, says he “feels very good” overall and is now embarking on a year-long health monitoring initiative. His identical twin brother, Mark, a former NASA astronaut who spent last year on solid ground, is one unique benefit he presents to NASA’s doctors.

Researchers will be able to detect any genetic alterations in Scott while he was in space by comparing the twins.

Meanwhile, here’s what NASA and the National Space Biomedical Research Institute say they’ll be looking for:

Brittle Bones

Astronauts no longer walk to enter the spaceship; instead, they float, reducing the load bearing capacity of the bones in the legs, hips, and spine.

This causes bone disintegration and calcium release, making the bone brittle and weak.

The production of kidney stones and bone fractures can both be exacerbated by calcium release.

Weak Muscles

Long-duration spaceflight causes the legs and back muscles to weaken or atrophy, which can result in fall-related injuries and mishaps during exploratory missions.

Face and legs puffy

Blood flows more freely in the upper body and less freely in the lower extremities in space.

Astronauts’ faces puff up and their legs become smaller in circumference while in space.

Smaller Heart

The heart doesn’t have to work as hard up there, which could reduce heart size over time.

There’s also the possibility that space radiation will harm endothelial cells, which line blood vessels, causing or hastening coronary heart disease.

Issues of balance

The inner ear, which is gravity-sensitive, is no longer working properly. Astronauts may endure disorientation, space motion sickness, and a loss of sense of direction early in the journey.

They must acclimatise to Earth’s gravity upon their return, and they may have difficulty standing up, stabilising their gaze, walking, and turning.

Astronauts get taller in space

Because of the discs in the spinal column, astronauts grow a little taller in space: The discs are slightly squeezed on Earth due to gravity. The discs expand because the compression is no longer existent in space. As a result, the astronaut’s spine lengthens and he grows taller.