What happens to the body after more than a year in space? – 09/27/2023 – Science

With a few handshakes, a brief photo session and a wave, NASA astronaut Frank Rubio said goodbye to the International Space Station (ISS), which had been his home for the past 371 days.

His departure from the orbital complex and his return to Earth mark the end of the longest space flight carried out by an American to date. His time in orbit—which surpassed the previous U.S. record of 355 consecutive days—was extended in March after the spacecraft in which he and his colleagues were returning home suffered a coolant leak.

The extra months in space saw Rubio log a total of 5,963 orbits around the Earth, traveling 253.3 million km. Still, he is about two months away from the record for the longest space flight in history by a human being — held by Russian cosmonaut Valeri Polyakov, who spent 437 days aboard the Mir Space Station in the mid-1990s.

With a huge smile on his face, Rubio was transported from the Soyuz MS-23 spacecraft after it landed safely on Earth leaving a cloud of dust near the city of Zhezkazgan in Kazakhstan.

Your long trip to space, however, will provide valuable information about how humans can cope with long-duration space flights and how best to counteract the problems they can present. He is the first astronaut to participate in a study examining how limited exercise done by astronauts with exercise equipment can affect the human body.

It’s information that will prove vital as humanity focuses on sending crews on missions to explore deeper into the Solar System.

A return trip from Mars, for example, should take around 1,100 days (just over three years) according to NASA’s current plans. The spacecraft the astronauts will travel in will be much smaller than the ISS, meaning smaller, lighter exercise machines will be needed.

Understand what is known to date about how space flight affects the human body.

MUSCLES AND BONES

Without the constant pull of Earth’s gravity on our limbs, muscle and bone mass quickly begin to decrease in space.

The most affected are the muscles that help maintain posture in the back, neck, calves and quadriceps — in microgravity, they no longer need to work as much and begin to atrophy. After just two weeks, muscle mass can drop by up to 20%. On longer missions, of three to six months, it can drop by 30%.

Likewise, because astronauts do not subject their skeletons to as much mechanical stress as when subjected to Earth’s gravity, their bones also begin to demineralize and lose strength.

Astronauts can lose 1 to 2% of their bone mass every month they spend in space and up to 10% over a six-month period (on Earth, older men and women lose bone mass at a rate of 0.5% to 1% every year). This can increase your risk of suffering fractures and increase healing time. It can take up to four years for bone mass to return to normal after returning to Earth.

To combat this atrophy, astronauts do 2 and a half hours a day of intense exercise and training while in orbit on the ISS. This includes a series of squats, deadlifts, rows and other exercises using a device installed in the ISS “gym.” They also exercise on a treadmill and stationary bike, and take supplements to help keep their bones as healthy as possible.

A recent study, however, showed that even this exercise regimen was not enough to prevent losses in muscle function and size.

The lack of more gravity to put pressure on their bodies can also cause astronauts to stand a little taller during their stay on the ISS, as their spines lengthen slightly.

This can lead to problems such as back pain while still in space and herniated discs once they return to Earth.

Before his return to Earth, Rubio himself said that his spine was growing. He said it could even help him avoid a common neck injury that astronauts can suffer when their spacecraft hits the ground. This is because they often try to get out of their seats to see what is happening.

“I think my spine has extended enough that I’m stuck in the seat padding, so I shouldn’t move too much,” he said.

WEIGHT LOSS AND FRIENDLY BACTERIA

While weight means very little in orbit — the microgravity environment means anything that isn’t tethered can float freely in the ISS habitat, including human bodies — maintaining a healthy weight is a challenge in orbit.

Although NASA tries to ensure its astronauts have a diverse range of nutritious foods, including, most recently, some salad leaves grown aboard the space station, the limited diet can still take its toll on an astronaut’s body.

The most extensive study of the effects of long-duration space flights was carried out by NASA astronaut Scott Kelly, who stayed aboard the ISS for 340 days while his twin brother remained on Earth. Kelly lost 7% of her body mass while in orbit.

Researchers who examined Kelly after his trip to the ISS also discovered that the bacteria and fungi that lived in his intestine had changed profoundly during the time he was in space.

Recent research shows that the composition and diversity of microorganisms that live in our bodies are key to health. The microbiota can influence the way we digest food, affect inflammation levels in our body and even change the way our brain works.

Researchers who examined Kelly after his trip to the ISS found that the bacteria and fungi living in his gut had changed profoundly compared to before he flew into space. This is perhaps not entirely surprising, given the very different food he ate and the change in the people he lived with — we get a lot of intestinal and oral microorganisms from the people we live with.

But radiation exposure and the use of recycled water, along with changes in your physical activity, may also have played a role.

VISION

On Earth, gravity helps force our body’s blood downward, and the heart pumps it to circulate. In space, however, this process gets messy (although the body adapts somewhat), and blood can accumulate in the head more than it normally would.

Some of this fluid can accumulate in the back of the eye and around the optic nerve, causing edema. This can lead to changes in vision, such as decreased clarity and structural changes in the eye itself.

These changes can begin to occur after just two weeks in space, and as time passes, the risk increases. Some of the vision changes reverse about a year after the astronauts return to Earth, but others may be permanent.

Exposure to cosmic microwave background radiation and solar energetic particles can also lead to other eye problems. Earth’s atmosphere helps protect us from these phenomena, but in space we don’t have this barrier.

Although spacecraft may carry shielding to help keep out excess radiation, astronauts aboard the ISS have reported seeing flashes of light in their eyes as cosmic rays and solar particles hit their retinas and optic nerves.

COGNITION

After his long stay on the ISS, it was discovered that Kelly’s cognitive performance changed little and remained relatively the same as his brother on the ground.

However, researchers noted that the speed and accuracy of Kelly’s cognitive performance declined over the course of about six months after landing, possibly as his brain readjusted to Earth’s gravity and his very different lifestyle. at home.

A study of a Russian cosmonaut who spent 169 days on the ISS in 2014 also revealed that some brain changes appeared to have happened during his time in orbit. It was discovered that there were changes in the levels of neural connectivity in parts of the brain related to motor function – that is, responsible for movement – ​​and also in the vestibular centers, which play an important role in orientation, balance and perception of our own movement.

This is perhaps not surprising, given the peculiar nature of weightlessness in space. Astronauts often have to learn how to move efficiently without gravity to ground them and adjust to a world where there are no ups or downs.

A more recent study has raised concerns about other changes in brain structure that may occur during long-term space missions. Cavities in the brain known as the right lateral ventricle and third ventricle can swell and take up to three years to return to normal size. These are areas responsible for storing cerebrospinal fluid, supplying nutrients to the brain and eliminating waste.

SKIN

Kelly’s skin became particularly clear while he was in orbit. He began experiencing increased sensitivity and skin rashes for about six days after he returned from the space station. The researchers speculated that a lack of skin stimulation during the mission may have contributed to the problem.

DNA

One of the most significant discoveries from Kelly’s extended trip to space was the effects it had on his DNA. At the end of each strand of DNA are structures known as telomeres, which help protect our genes from damage. As we age, DNA copies itself to produce new cells. And with each copy that DNA makes of itself, telomeres become shorter – like copying a copy of an image on paper, it becomes less clear.

Research carried out with Kelly and other astronauts revealed that space travel appears to alter the length of their telomeres.

“The most impressive thing was the discovery of significantly longer telomeres during spaceflight,” says Susan Bailey, a professor of environmental and radiological health at Colorado State University who was part of the team that studied Kelly and her brother.

She also did separate studies with 10 other astronauts who participated in shorter missions of about six months. “Also unexpected was that telomere length decreased rapidly upon return to Earth for all crew members. Astronauts in general had more short telomeres after spaceflight than before, something of particular relevance to long-term health and safety.” aging trajectories.”

It’s not yet known exactly why this happens, she says.

“We have some leads, but other long-term crew members – like Rubio, who spent a year in space – will be key to really characterizing and understanding this response and its potential health outcomes.”

One possible cause could be exposure to the complex mix of radiation in space. Astronauts who experience prolonged exposure while in orbit show signs of DNA damage, she says.

There were also some changes in gene expression – the mechanism that reads DNA to produce proteins in cells – observed in Kelly that may be related to his trip to space.

Some of these are connected to the body’s response to DNA damage, bone formation, and the immune system’s response to stress. Most of these changes, however, returned to normal six months after his return to Earth.

IMMUNE SYSTEM

Kelly received a series of vaccines before, during and after her trip to space and her immune system responded normally. But Bailey’s research has found that astronauts experience some decreases in their white blood cell counts. This change is in line with the radiation doses they receive while in orbit, she says.

However, there are still many questions to be answered about the impact that space travel could have on a large-brained, bipedal species that evolved here on Earth.

As Rubio recovers from his 371 days in space, researchers will no doubt analyze his scans to see what else they can learn.