NASA astronaut Frank Rubio just returned from a record-breaking 371 days in space aboard the International Space Station, and the trip may have changed his muscles, his brain, and even the bacteria living in his gut.
After a few greetings, a brief photo session and a wave, Astronaut Rubio said goodbye to the football stadium-sized collection of modules and solar panels that had been his home for more than a year.
His departure from the International Space Station and return to Earth marks the end of the longest solo space flight by an American to date.
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The time he spent in orbit broke the previous US record of 355 days, and was extended in March after it was discovered that the spacecraft he and the rest of the crew were supposed to use to return home was leaking coolant.
The additional months spent in space allowed Rubio to collect a total of 5.963 revolutions around the Earth and travel 253,3 million kilometers.
However, he is still about two months short of breaking the absolute record - Russian cosmonaut Valery Polyakov spent 437 days on the Mir space station in the mid-XNUMXs.
With a big smile on his face, Rubio was carried off the Soyuz MC-23 spacecraft after it landed safely on Earth in a cloud of dust near the city of Zheskazgan on the Kazakh steppe.
Being in the low-gravity environment of the International Space Station for so long must have taken its toll on his body, as rescue teams had to lift him out of the capsule.
An extended stay in space will provide useful insights into how humans cope with long periods of spaceflight and how best to combat the problems that may arise.
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Rubio is the first astronaut to participate in a study that examines how exercise with reduced gym equipment can affect the human body.
It's information that will prove crucial as humans now want to send crews into space exploration much further into the solar system.
A return from Mars, for example, is expected to take 1.100 days (just over three years), according to current plans.
The spacecraft humans will travel on will be much smaller than the International Space Station, which means smaller, lighter exercise equipment will be needed.
But keeping in shape aside - what exactly does spaceflight do to the human body?
Muscles and bones
Without the force of gravity exerting constant pressure, our limbs, muscles and bone mass slowly begin to shrink in space.
The muscles that help maintain our posture in the back, neck, calves and quadriceps are the most affected - in microgravity they don't have to work nearly as hard and so begin to atrophy.
After just two months, muscle mass can drop by as much as 20 percent, and on longer missions lasting three to six months, it can drop by up to 30 percent.
Similarly, because astronauts do not subject their skeletons to as much mechanical stress as they do under Earth's gravity, their bones also begin to demineralize and lose strength.
Astronauts lose one to two percent of bone mass each month they spend in space, and up to 10 percent in each six-month period (on Earth, older men and women lose bone mass at a rate of 0,5-1 percent each year).
This can increase the risk of fracture and increase the amount of time needed to heal.
It can take up to four years for their bone mass to return to normal upon returning to Earth.
To combat this, astronauts must do 2,5 hours of exercise and intense training each day while in orbit on the International Space Station.
These include sets of squats, deadlifts, incline rows and bench presses with the help of exercise machines installed in the International Space Station "gym", along with regular sets on a treadmill or exercise bike.
They also take dietary supplements that help their bones stay as healthy as possible.
A recent study, however, pointed out that even this exercise regimen is not enough to prevent loss of muscle function and size.
She recommended testing whether heavier weight in resistance exercises and high-intensity training could help prevent this muscle loss.
The absence of gravity pulling their bodies down can also mean that astronauts find that they grow a little taller during their time on the International Space Station as their spines elongate slightly.
This can lead to problems with back pain while in space and bulging discs once back on Earth.
During a briefing on the International Space Station before returning to Earth, Rubio himself said that his spine is growing and that it could help him avoid the frequent neck injury that astronauts experience when their spacecraft hits the ground if they try to twist their necks. in the seats to see what's going on.
"I think my spine has elongated just enough to fit into the perforation of the seat, so I won't be moving much," he said.
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Weight loss
Although weight means very little while in orbit—the microgravity environment means that anything untethered can float freely around the space of the International Space Station, including human bodies—maintaining a healthy weight is a challenge while in orbit.
Although NASA tries to ensure that astronauts have a varied range of nutritious diets, including most recently a few lettuce leaves grown on the space station itself, it can still take a toll on an astronaut's body.
Scott Kelly, the NASA astronaut who participated in the most expensive study of the effects of long-duration spaceflight after staying aboard the International Space Station for 340 days while his twin brother stayed home on Earth, lost 7 percent of his body mass while in orbit.
Researchers who studied Scott Kelly after his trip to the International Space Station found that the bacteria and fungi living in his intestines had fundamentally changed compared to the period before he flew into space.
At
On Earth, gravity helps the blood in our bodies move downward while the heart pumps it back up.
In space, however, this process gets mixed up (although the body adapts somewhat) and blood can accumulate in the head more than it normally would.
Some of this fluid can collect behind the eye and around the optic nerve, leading to edema.
This can also lead to changes in vision such as reduced sharpness and structural changes in the eye itself.
These changes can begin to occur after as little as two weeks in space, but as time passes, that risk increases.
Some of the vision changes reverse within a year of the astronauts returning to Earth, but others may be permanent.
Exposure to galactic cosmic rays and energetic solar particles can also lead to other eye problems.
Earth's atmosphere helps protect us from them, but once you're in orbit on the International Space Station, that protection disappears.
And while spacecraft may have shields to shield us from excess radiation, astronauts on the International Space Station have reported seeing flashes of light in their eyes as cosmic rays and solar particles hit their retinas and optic nerves.
Nerve displacement
After his long stay on the International Space Station, however, it was found that Kelly's cognitive performance had changed very little and remained relatively the same as that of his brothers on Earth.
However, the researchers noted that the speed and accuracy of Kelly's cognitive performance did increase about six months after he landed, 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 International Space Station in 2014 also showed that some changes occur in the brain itself while in orbit.
It found that there were changes in neural connectivity levels in parts of the brain related to motor function - in other words, movement - and also in the vestibular cortex, which plays an important role in orientation, balance and the perception of our own movement.
This is perhaps not surprising, given the unusual nature of weightlessness in space; astronauts often have to learn how to move efficiently without gravity anchoring them to anything and adapt to a world where there is no up and down.
A more recent study has raised concerns about other changes in brain structure that may occur during long-duration space missions.
The cavities in the brain known as the right lateral and third ventricles (responsible for storing cerebrospinal fluid, providing nutrients to the brain and removing waste) can swell and take up to three years to return to normal size.
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Good bacteria
It is obvious based on research from recent years that an important key to good health is the composition and diversity of microorganisms that live on and in our bodies.
This microbiota can affect the way we digest food, affect the levels of inflammation in our bodies and even alter the way our brains work.
Researchers who studied Kelly after his trip to the International Space Station found that the bacteria and fungi living in his gut had changed significantly compared to the period before he flew into space.
That may not be too surprising, given the very different food he ate and the changes in the people he spent his days with (we pick up a frightening amount of intestinal and oral microorganisms from the people we live next to).
But radiation exposure and the use of recycled water, along with changes in his physical activity, may have played a role.
Skin
While there have been five NASA astronauts to date who have spent more than 300 days in orbit, we can once again thank Kelly for his insight into how his skin behaved while in orbit.
It turned out that his skin became more sensitive and developed a rash about six days after returning from the space station.
The researchers speculated that the absence of skin stimulation during the mission may have contributed to his skin problem.
Geni
One of the most significant findings from Kelly's extended space travel was the effects it had on his DNA.
At the end of each strand of DNA are structures known as telomeres, which are believed to protect our genes from damage.
As we age, they shorten, but research on Kelly and other astronauts has found that space travel appears to change the length of those telomeres.
"Most striking, however, was the discovery of significantly longer telomeres during the spaceflight itself," says Susan Bailey, a professor of environmental health and radiology at Colorado State University who was part of the team that studied Kelly and his brother.
She did separate studies on 10 other unrelated astronauts who participated in shorter missions of about six months.
"It was also unexpected that telomere length rapidly decreased upon return to Earth in all crew members.
Of particular importance to long-term health and aging trajectories, astronauts generally had many more short telomeres after spaceflight than before.
Why exactly this happens scientists are still trying to unravel, she says.
"We have some clues, but more long-term crew members — like Rubio, who spent a year in space — will be critical to characterizing and understanding this reaction and its potential health outcomes."
One possible cause is exposure to a complex mix of radiation while in space.
Astronauts who experience long-term 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 make proteins in cells - seen in Kelly that could be related to his space travel.
Some of them had to do with 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 within six months of his return to Earth.
The immune system
Kelly received several vaccines before, during and after the space trip and his immune system appeared to be responding normally.
But Sarah Bailey's research has shown that astronauts do experience some declines in white blood cell counts that are consistent with the radiation doses they received while in orbit.
There are still many questions that need answers, however, about what impact space travel might have on bipedal species with big brains that have evolved to live on Earth.
As Rubio recovers from his 371 days in space, researchers will no doubt carefully sift through his medical tests, blood samples and scans to see what else they can learn.
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