Why astronauts grow up to five centimeters when they go into space

Why astronauts grow up to five centimeters when they go into space

Traveling off the ground causes a loss of muscle mass, visual problems, and circadian rhythm disorders.

The Japanese astronaut Norishige Kanai announced Tuesday that he had grown nine centimeters in space during his three weeks at the International Space Station (ISS). "I'm a little concerned about whether I'll go into the Soyuz ship seat when I get back," he told on his Twitter. This ship is the one that takes the astronauts from Earth to the ISS and vice versa, and their seats have a height limit. But this Wednesday, after the news has been around the world, Kanai has apologized for an error in the measurement: it has really only grown two centimeters.

Astronauts grow in space between two and five centimeters. This is due to the absence of gravity, which causes the vertebrae to separate and the spine to expand. But when they return to Earth, in a short time they return to their original height. "The discs are like sponges", explains the founder and first director of the Museu de la Ciencia de Barcelona (current CosmoCaixa), Rafael Clemente. This industrial engineer and specialist in dissemination on astrophysics ensures that the spine does not lengthen endlessly: "As you are in space a month that one year, there will come a time when you won't grow any more."

Since human beings arrived in space, more than 50 years ago, several medical studies have been conducted to determine how it affects the human body to leave the earth. Scott Kelly was the first American to spend almost a year in space aboard the International Space Station. NASA studied how the trip affected his comparing health with that of his twin brother, who stayed on Earth.

One of the most damaging effects of traveling to space is that you lose a lot of calcium. There it floats, and moving requires much less effort. While an elderly person on earth can lose 1% bone mass per year, in space that amount is volatilized in a month. In addition, inside the capsule the astronauts do not give them the sun, an important source of vitamin D. "What happens is very similar to what happens to older people who are bedridden: suffer from problems of osteoporosis or calcium loss" , Clemente stresses. To alleviate this problem, they have a very intense exercise program throughout the day: they spend hours on the static bike or in the weight lifting simulator.

The lack of gravity also produces atrophy in the muscles and the limbs lose volume. To avoid this, according to Clemente, the Russians used years ago the Penguin costume, formed by trousers with elastic straps to the feet that forced them to make effort with the legs to keep them stretched. "When they land after a long trip, they practically have to pull them in their arms and then sit them down in a chair, they take days to re-acquire muscle tone," he explains.

Two-thirds of the astronauts return from space with myopia, although many of them are pilots who used to enjoy a perfect vision. A study presented in 2016 at the American Society of Radiology's annual meeting reveals that this is due to changes in cerebrospinal fluid, the central nervous system fluid, due to the lack of gravity.

It's not always easy to take off. There are astronauts who have dizziness during the first hours of travel. Frank Borman, the commander of Apollo 8 — the first mission to go to the moon — vomited twice on the way out. At 24 hours he recovered and during the rest of the mission he had no symptoms. But for NASA, "the most dangerous aspect of traveling to Mars is space radiation." Astronauts in space receive up to ten times more radiation than on Earth. Exposure to radiation may increase your risk of cancer, causing degenerative diseases such as cataracts or heart and circulatory diseases.

In addition to physiological problems, it can also have psychological consequences. Having four people stuck in a capsule for six months can cause incompatibilities between them. For this reason, the expedition teams are carefully selected taking into account that they can work effectively as a team. "Misunderstandings can affect the performance and success of the mission," NASA explains on its website. To this we must add possible disorders of circadian rhythm, because, according to Clement, "in an orbital ship you can see a sunrise and a sunset every 90 minutes. Therefore, the 24-hour rhythm is dismantled. "

Knowing how the human body reacts to the conditions of space is useful in the face of future missions, when space travel is measured in months or years. For example, on the surface of Mars, it would live in about a third of the Earth's gravity. For this reason, NASA works in the elaboration of a medical program to compensate for the counterproductive effects of weightlessness.