26 Things That Happen To Your Body In Space

Have you ever wondered what happens to the human body in the zero-gravity environment of space?

From changes in height to weakened bones, the effects of microgravity and radiation can be strange and fascinating.

Read on to learn 26 ways space affects the body and mind—you’ll be amazed at what happens to astronauts during months or years in orbit!

1. Bones Lose Density

Photo By Endocrine

On Earth, the human skeleton evolves under constant gravitational force. In the free-fall of space, astronauts experience as much as 2% bone loss per month as the body scrambles to adjust. Without the pull of gravity, bones lose essential mineral density and become brittle and weak. Astronauts combat this by eating diets rich in calcium and through rigorous exercise regimes while in space.

2. Muscles Atrophy

muscle atrophy
Photo By The PTDC

On Earth, the human body constantly works against gravity. In the weightlessness of space, however, the body doesn’t need to exert as much effort to move and maintain posture. Without regular intensive exercise, astronauts can lose up to 20% muscle mass during spaceflight. This muscle atrophy affects the legs, back, and arm muscles the most. Astronauts work out for 2 hours per day on specialized equipment to prevent muscle loss in microgravity.

3. Body Elongates

human floating in space
Photo By TS2

Without the constant downward pull of gravity, the spine can elongate up to 3%. Astronauts can grow up to 3 inches taller in space. However, this height gain is temporary. Upon return to Earth, the spine compresses back to its original length. While a couple of extra inches sounds nice, this spinal elongation causes back pain for some astronauts. The body adapts to microgravity quickly, so most astronauts grow used to their new height after some time in space.

4. Face Puffs Up

astronaut puffy face
Photo By Geek Wire

Another visible effect of microgravity is facial puffiness. Just like the rest of the body, fluids shift upwards in zero gravity. This causes facial tissues to swell. Astronauts can look different after spending some time in space. The puffiness is often noticeable around the sinuses, cheeks and neck. But not to worry, the facial swelling goes away after returning to Earth. Gravity pulls the fluids back down. So while astronauts may return a bit taller, their facial features go back to normal after readjusting to life with gravity.

5. Blood Volume Decreases

plasma volume
Photo By The Blood Project

One effect of microgravity is a decrease in blood volume. Without the pull of gravity, bodily fluids shift around. This causes a reduction in the amount of blood plasma. The body senses the drop in volume and counters it by eliminating fluids. Astronauts can lose up to 22% of their blood volume in space.

The decrease in blood volume leads to symptoms like lowered blood pressure and dizziness upon returning to Earth. It takes some time for the body to rebuild its blood supply. Drinking plenty of fluids helps speed up the recovery process. Knowing these effects ahead of time allows astronauts to be prepared for the changes.

6. Heart Shrinks

human heart shrink in space
Photo By Lab Roots

Another effect of microgravity is that the heart will shrink in size. On Earth, the heart has to pump against gravity to move blood through the body. In the microgravity of space, the heart doesn’t have to work as hard. This decreased effort causes the heart muscle to atrophy. Studies show that astronauts’ hearts can lose up to 20% of their muscle mass on spaceflights.

The less strenuous conditions cause the heart to become smaller and weaker. After returning to Earth, it takes a while for the heart to rebuild and strengthen its muscles again through exercise. Knowing this effect, astronauts do resistance training in space to try to counteract the atrophy. However, some muscle loss is unavoidable, so they must ease back into training upon return.

7. Blood Pressure Drops

nurse recording blood pressure
Photo By Heart

Going to space also causes blood pressure to decrease. On Earth, the blood has to circulate against the force of gravity, so the pressure is higher. In the microgravity environment, there is no gravity pulling the blood down, so the pressure drops. Studies have recorded drops in both the systolic (maximum) and diastolic (minimum) blood pressures in astronauts after entering microgravity.

One study on the Space Shuttle found an average drop of 15 mmHg systolically and 10 mmHg diastolically. The body adapts to this change while in space. But when returning to Earth’s gravity, it has to readjust again which can cause dizziness. To prepare for return, astronauts drink more fluids and use compression garments to help control blood pressure changes.

8. Red Blood Cell Count Rises

red blood cells
Photo By Self Decode

Microgravity also causes the number of red blood cells in the body to increase. On Earth, the bone marrow makes a hormone called erythropoietin that tells the body to produce more red blood cells. In space, the body doesn’t need to work as hard to pump blood against gravity, so erythropoietin levels rise. This signals the body to produce more red blood cells.

Studies have shown red blood cell counts increasing by 10-15% in astronauts. However, the body adapts and erythropoietin levels stabilize over time. When astronauts return to Earth, their red blood cell counts slowly return to normal as the body adjusts to gravity again.

9. Immune System Weakens

astronaut in space freezing
Photo By Business Insider

The immune system also weakens in the microgravity environment of space. Scientists believe this is caused by physiological changes and stress. Studies have shown that the activity of natural killer cells, which help the immune system fight infections and cancer, decreases in astronauts in space. The ability of T-cells to activate and respond to threats also declines. In addition, bacteria have been found to grow faster in microgravity.

The combination of a weakened immune system and increased microbial growth creates a greater risk of astronauts getting sick. However, research is still ongoing to fully understand the impacts of space on immunity. Developing countermeasures to boost immunity is an active area of focus for future long-duration space missions.

10. Sleep Cycle Disorders

astronaut suffering with sleep problems
Photo By CNN

Another issue astronauts face is disrupted sleep cycles. The lack of a 24-hour light/dark cycle in space confuses the body’s circadian rhythm. The constant noise and temperature changes on spacecraft also impact sleep. Astronauts have reported only sleeping around 6 hours per night during spaceflight, with frequent waking through the night.

Poor and insufficient sleep impairs cognition, mood, and alertness. This can jeopardize astronaut performance and mission safety. Developing techniques to improve sleep quality during space travel is an important goal. Scheduling mission tasks around optimal sleep periods and using eye masks, ear plugs, and sleep stations aim to help. However, more work is needed to enable sound slumber for interplanetary travelers.

11. Increased Flatulence

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Flatulence and intestinal gas are also common complaints during spaceflight. The microgravity environment causes a redistribution of gases and fluids in the body. This slows digestion and can lead to more gas being produced and trapped. The low-fiber space diet also plays a role. The gases cause uncomfortable bloating and borborygmi (rumbling sounds).

Passing the gas is more difficult in microgravity. The usual convection currents that help move things along in gravity are absent. Astronauts report increased flatulence that they cannot easily expel, resulting in feeling gassy. Improving diet, probiotics, and exercise aims to lessen the issue. However, flatulence remains an annoying reality of life in space that astronauts must deal with.

12. Decreased Sense of Taste

astronauts eating in space
Photo By Astronaut Food

Another effect of microgravity is a dulled sense of taste. Fluid shifts affect the mucous membranes in the sinus cavities, which are linked to our abilities to smell and taste. With congestion in these areas, smell and taste receptors become less sensitive. Foods tend to taste more bland and have a more uniform texture. Spicy foods take on a metallic flavor.

Astronauts often add more spices and condiments to try to liven up their meals. Colds and sinus congestion on Earth have a similar muting effect on smell and taste. After returning to Earth, astronauts report a heightened sense of taste and smell for a few weeks. Their senses return to normal after readjusting to gravity.

13. Congestion Due to Fluid Shift

water in space
Photo By John Lamb / Getty Images

Fluid shifting in the body also leads to congestion issues for astronauts. In zero gravity, body fluids that normally pool in the legs and lower extremities redistribute throughout the body. This increased fluid in the upper body and head causes congestion of the nasal passages and sinuses. Astronauts describe feeling like they have head colds for the first few days in space.

They also experience stuffiness in the ears from the fluid buildup. The congestion subsides after the body adjusts its fluid volumes. However, astronauts continue to feel some head fullness and nasal congestion throughout their missions due to the lack of gravity pulling fluids down. After returning to Earth’s gravity, it takes a few days for fluids to redistribute back to the lower extremities and relieve the congestion.

14. Increased Urine Output

how astronauts go to the bathroom
Photo By The Wire

Another effect of fluid shifts in space is increased urine output. On Earth, the kidneys adjust urine production to maintain proper fluid levels throughout the body. In zero gravity, this system gets disrupted. The fluid shift towards the upper body tricks the kidneys into thinking there is too much fluid volume. They excrete more urine to lower fluid levels.

Astronauts urinate frequently during the first few days of spaceflight to reduce the excess fluid. Their bodies eventually reach a new equilibrium with lower overall fluid volume. However, astronauts continue to produce more urine throughout their missions as their kidneys adapt to the fluid shifts caused by microgravity.

15. Deconditioning of Posture Muscles

woman reading in the international space station
Photo By Fox Weather

On Earth, the posture muscles constantly work against gravity to maintain our body’s alignment. In the free-fall of space, these muscles have very little to do. Without gravity pulling us down, the body does not need to engage the muscles to the same degree. After months in space, the posture muscles become deconditioned and weaken from disuse.

Astronauts can lose up to 20% muscle mass during long-duration missions. This makes it challenging for them to stand and move when they return to Earth. Physical exercise and resistance training help counteract muscle atrophy in space. But some deconditioning is unavoidable, and astronauts may need rehab to regain strength after prolonged flights.

16. Balance Disorders

astronaut being carried
Photo By NASA / Bill Ingalls

Living in microgravity also affects astronauts’ sense of balance. On Earth, the brain uses gravity, vision, and sensory information from the inner ear to orient the body. In space, gravity cues are absent, and fluids shift in the inner ear, causing space motion sickness. After returning to Earth, astronauts often struggle with balance problems and dizziness as their brains readjust.

Movements and head positions that were easy in microgravity require effort and concentration. Vestibular rehabilitation therapy helps the brain relearn how to balance the body under gravity. Exercises include building tolerance to head movements and visual distortion. Balance and coordination gradually improve over weeks or months, though some astronauts experience lasting effects.

17. Motion Sickness

woman suffering motion sickness
Photo By Carl Smith

Experiencing microgravity can wreak havoc on astronauts’ sense of balance and spatial orientation. About half of astronauts experience space motion sickness in the first few days in orbit as their vestibular system adapts to weightlessness. Nausea, vomiting, headaches, and vertigo make it difficult to work and move around. Medications like promethazine or scopolamine provide some relief.

Over time, astronauts adapt as the brain creates a new internal model of the body’s orientation. But when they return to Earth, gravity cues conflict with this new model. Sudden movements like walking down stairs or looking up and down can trigger motion sickness until the brain readjusts to gravity again. This takes days or weeks, though some astronauts have lingering motion sickness after spaceflight.

18. Radiation Exposure

effects of radiation to the body
Photo By CDC

Outside the protection of Earth’s magnetic field and atmosphere, astronauts are exposed to ten times more radiation than on Earth. The ISS sits within the Van Allen radiation belt, a zone of charged particles from the solar wind and cosmic rays. Prolonged exposure increases risks of cancer, central nervous system effects, and degenerative diseases.

Radiation can penetrate through the hull of spacecraft and spacesuits. Short missions of a few weeks are less concerning, but for longer missions, there are serious health risks. Shielding helps block radiation but adds weight. Medications and dietary supplements like antioxidants may offer some protection. More research is still needed to mitigate radiation risks for future long-duration missions to the Moon or Mars.

19. Cancer Risk

astronauts in space
Photo By Slash Gear

Radiation exposure during space travel increases the lifetime risk of cancer for astronauts. Charged particles from cosmic rays and solar flares can damage DNA and cause cell mutation. Astronauts receive over ten times the radiation dose on Earth annually. The lifetime risk of fatal cancer for astronauts is estimated to be between 1% and 19% depending on age, gender, and mission duration. Younger astronauts and women have higher risks.

Missions beyond low Earth orbit like to the Moon or Mars would expose astronauts to even more galactic cosmic radiation and solar particle events. Current spacecraft shielding is unable to fully block the most damaging types of radiation. More research on biological countermeasures like drugs and dietary antioxidants is needed to protect astronauts on future long-duration missions.

20. Vision Changes

astronaut vision change
Photo By Space

The microgravity environment in space causes fluid shifts in the body that increase pressure in the head. This leads to vision problems for many astronauts. More than 20% experience degraded visual acuity and experience blurred or distorted vision during long-duration missions. The shape of the eyeball elongates in zero gravity, which can cause far-sightedness.

Increased fluid pressure also compresses the optic nerve, leading to swelling of the optic disc. Astronauts report spots or flashes of light in their vision, likely caused by cosmic radiation interactions. Post-flight, most vision issues subside, but some astronauts have reported permanent degradation like scotoma. Future missions to Mars lasting 2-3 years could pose even greater risks of permanent vision damage for astronauts.

21. Intracranial Pressure Rises

Intracranial pressure
Photo By Very Well Health

In addition to vision changes, the fluid shift in zero gravity causes increased intracranial pressure. On Earth, gravity pulls fluids like blood downwards, but in space, this does not occur. Research during long-duration missions on the ISS reveals that astronauts’ intracranial pressure can rise over 20 mmHg above pre-flight supine measurements. This elevated pressure places dangerous strain on blood vessels in the head and eyes.

Astronauts report symptoms like headache, tinnitus, nausea, photophobia, and irritability that may indicate high intracranial pressures. Measures like strict sleep positioning, medications, and lower body negative pressure have been tested to counteract the fluid shift. However, more research is needed to protect astronauts’ vision and brain health during future long-duration space travel.

22. Increased Infection Risk

infographic on the effects of space on the body
Photo By Innova Space

Microgravity and cosmic radiation combine to weaken astronauts’ immune systems in space. Studies show decreased production of disease-fighting T-cells, slower wound healing, and reactivation of latent viral infections. The closed environment of a spacecraft and reduced diversity of microbes also limit immune system stimulation. With a suppressed immune system, dormant viruses like chickenpox or shingles can reactivate and make astronauts sick.

Bacterial infections are also a major concern, especially with limited medical care available during long-duration missions. Preventive measures include screening astronauts’ microbiomes before flight and ensuring rigorous hygiene and frequent cleaning of surfaces. But more research on in-flight immune function will be key to keeping astronauts healthy on future long-term space voyages.

23. Bone Marrow Alterations

bone marrow alterations in space
Photo By Space

Long-term exposure to microgravity causes changes to bone marrow stem cells in astronauts. Studies on mice show that just 9 days in space alters the hematopoietic stem cells that produce red and white blood cells. This affects the cells’ ability to regenerate and results in improper production of blood cell types. Similar effects have been observed in astronauts on 6-month missions to the ISS.

The mechanisms behind these spaceflight-induced marrow changes are still unclear. However, altered marrow function could impact astronauts’ ability to fight infection and deliver oxygen on long voyages. More research is needed to understand if these effects are reversible upon return to Earth gravity. Developing effective countermeasures to mitigate changes to bone marrow could be vital for maintaining astronaut health on missions deeper into space.

24. DNA Damage

dna damage
Photo By The Scientist

Microgravity and cosmic radiation in space can cause genetic damage to astronauts. Studies show increased DNA damage in astronauts after short-duration spaceflights. Cosmic radiation exposure is known to break DNA strands and cause mutations. Microgravity also alters DNA repair mechanisms in cells. This combined effect increases overall DNA damage during space travel.

Over time, accumulated DNA damage may elevate cancer risk in astronauts. NASA research found chromosomal abnormalities in astronauts after long-duration missions. More studies are underway to assess the impacts of space radiation on DNA and cancer risk. Developing radiation shielding and countermeasures to mitigate this DNA damage could be critical for enabling safe, long-term space exploration.

25. Cognitive Declines

cognition decline
Photo By Space

The space environment can also lead to declines in cognitive performance. Studies show astronauts experience deficits in memory, attention, and reaction time after spaceflight. One theory is that increased exposure to cosmic radiation in space damages neurons in the hippocampus, a brain region critical for memory formation. Microgravity also alters blood flow to the brain which may impact cognitive function.

Fatigue from space motion sickness early in flight likely contributes as well. More research is still needed to fully understand these cognitive impacts of space travel. Developing effective countermeasures to mitigate cognitive declines could be vital for maintaining astronaut health and performance during long-duration missions. Things like regular cognitive training, medications, and nutrition strategies may help offset these concerning cognitive effects of space travel.

26. Emotional Effects

astronaut mental health
Photo By Canadian Space Agency

The isolation and stress of spaceflight can also take a toll emotionally. Astronauts have reported feelings of depression, anxiety, irritation, and interpersonal conflicts during missions. The tight living quarters, lack of privacy, disrupted sleep cycles, and dangers of space all contribute to unique stressors. Separation from family and friends for extended periods also increases homesickness and loneliness.

NASA research shows that some astronauts struggle with post-flight re-adjustment issues as well. After returning home, they can experience mood instability, relationship conflicts, and even clinical disorders like depression or post-traumatic stress. Ongoing psychological screening and support pre-flight, in-flight, and post-flight are now routine practices to help astronauts cope with these emotional challenges of space travel.


What Happens to an Exposed Body in Space?

An exposed body in space would undergo some gruesome effects without a protective spacesuit. The lack of atmospheric pressure would cause gases to expand, which can rupture skin and tissue. Body fluids would boil and evaporate away. Without oxygen, a person would lose consciousness within 15 seconds. Ultimately, exposure leads to asphyxiation and death.

What Happens to a Body in Space Without a Spacesuit?

Without a spacesuit, a body would swell, blood would boil, and lungs would likely rupture. The water in the body would vaporize, and the body would mummify over time. Death would occur quickly from asphyxiation, with exposure leading to unconsciousness in just 15 seconds.

How Are Bodies Disposed of in Space?

Bodies are not typically disposed of in space. Any human remains are returned to Earth for proper burial. However, if someone did die in space, the body would likely be stored in the spacecraft until it could be returned to Earth. Leaving remains in space could pose health hazards for fellow astronauts.

What Would Happen if You Took Your Helmet off in Space?

Taking your helmet off in the vacuum of space would be fatal within minutes. Air pressure would rapidly escape from your lungs, blood would boil, and exposed areas would swell. You would lose consciousness due to a lack of oxygen in about 15 seconds. Death would follow shortly after.


The human body is not built to withstand the extreme conditions of space. Without the protection of a spacesuit, exposure leads to swelling, boiling of fluids, asphyxiation, and ultimately death within minutes. Bodies are returned to Earth for proper disposal. Leaving remains in space poses health risks and is avoided. In summary, space is a very lethal environment for an unprotected human body.

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