Long space flights threaten astronauts with critical changes in the human body, such as an increased risk of DNA damage. But the list of negative aspects of the spaceflight is much longer.
An astronaut in space – artistic drawing. How does human body change while staying in space for long time? Image credit: Monica Garniga via Unsplash, free license
NASA plans to start colonizing the Moon soon, and then, possibly within the next decade, the first astronauts will land on Mars. The far-reaching prospect of such an initiative is the possibility that humanity will eventually be able to populate other worlds in the solar system.
However, in order to reach them, it is necessary to overcome huge distances traveling in space. But what will happen to the human body during a long space journey?
An astronaut – artistic impression. Image credit: Bradley Dunn via Unsplash, free license
Why our bodies are not suitable for space travel?
According to the facts established by numerous research studies, a long stay in space is not good in terms of human health.
Humans are adapted to live in the favorable conditions of our planet, and nature has not prepared the human body for long-term stay in space. Some scientists even believe that in order for humans to live on Mars or other worlds in the solar system, it will be necessary to change our DNA.
The thing is, space is a really, really dangerous place for humans. Here, we can talk about microgravity's negative effects (a state of almost complete weightlessness in a spacecraft) and dangerous cosmic radiation on the human body.
So what happens to the human body during long periods of time in space? Below you will find the most dangerous effects of space travel explained.
Astronaut replaces Space Station components. Image credit: NASA
How does the human body change in space?
- Loss of muscle mass
Muscles need Earth's gravity to grow and function normally. In weightlessness, muscles quickly atrophy, and muscle mass decreases. According to research, a person can lose up to 20% of their muscle mass in just 5 days in microgravity. This loss is especially noticeable in the legs and back.
- Loss of bone mass
The maintenance of the normal condition of the human skeleton – all of its bones – directly depends on the Earth's gravity. Studies show that after spending more than 6 months in space, bones become brittle and can break very easily.
Bone tissue in space does not break down as quickly as muscle, but this causes another negative issue. Due to the depletion of bone mass, too much calcium enters the blood, which in particular leads to the rapid formation of kidney stones. The bones of the legs and lumbar spine suffer the most from space conditions, as research shows.
- Vision problems
The eyes are one of the most complex organs in the human body. Outer space can cause serious damage to our organs of vision. For example, the nerves in the back of the eye can change and deform, causing severe vision loss.
Earth's gravity allows the eyeballs to move normally in the eye sockets and maintain their position. However, a long stay in a state of weightlessness, according to scientists, leads to changes in the position of the eyeballs and the speed of their movement. Thus, a person loses the ability to observe certain objects normally.
Also, due to the conditions of outer space, eye tissues can be severely damaged, and after prolonged exposure, a person would see the surrounding world very dimly.
- Back pain
Even now, astronauts returning from the International Space Station often complain of severe back pain. The reason is the negative effect of microgravity on the human spine.
Due to the Earth's gravity, the spine is compressed and it takes on a slightly curved shape. But in space, the spine straightens, and the connections between the vertebrae become less strong.
Scientists believe that short flights in space will not cause strong changes in the spine. But this cannot be said about long flights. During long space trips, the muscles supporting the vertebrae will weaken, and the intervertebral discs, which act as shock absorbers, will begin to “fall apart”. Back pain can become very unbearable and this condition can affect whether a person can move normally at all.
Blood test. Image credit: Piqsels, free public domain licence
- Decreased immunity
Space radiation, microgravity, and the physical and psychological stress of long-term spaceflight can severely weaken the immune system. And this means that the human body becomes less resistant to various diseases.
There is a chance that microbes could cause irreparable damage to the body after a longer stay in space, which in turn could lead to very serious diseases.
- Problems with the cardiovascular system
The heart is highly dependent on gravity, as it allows this organ to contract normally and move blood through the body. In weightlessness, if the flight lasts for a very long time, this function is disrupted, which can negatively affect the general physical condition of a person. Scientists also believe that the risk of blood clots in the blood vessels increases during a long space flight.
A doctor reviews the results of chromosome and DNA testing. Image credit: MSGT Dave Nolan, USAF / Public Domain
- DNA damage
According to some studies, space travelers will be at increased risk of DNA damage due to cosmic radiation and low gravity. Radiation can directly damage DNA strands, and weightlessness can interfere with DNA's natural repair.
Scientists believe that long space flights can lead to the accumulation of genetic mutations that can lead to a number of dangerous diseases, including cancer.
- Damage to the digestive system
The human gastrointestinal tract is home to trillions of microbes that can affect a person's digestive function, immune system, and metabolism.
According to the researchers, the gut microbiome is constantly changing in response to external factors such as dietary changes and general body stress. During a long flight into space, these changes will be very dangerous for humans. For example, studies have found less diverse microbial populations in the guts of astronauts. And often among them are those microbes that contribute to intestinal inflammation.
- Changes in the brain
Scientists believe that deep space travel can “reprogram” the brain, and the very low gravity is likely the culprit.
Due to weightlessness, the cerebrospinal fluid that supplies nutrients to the brain and spinal cord begins to change. This can cause changes in the shape and weight of white and gray matter in the brain. That is, the structure and activity of the human brain can change. However, scientists do not yet know how harmful these changes are to humans.
Also, research shows that long flights into space can change how different parts of the brain interact with each other. It is also not yet clear how exactly it would change the human personality.
Written by Alius Noreika