The Health Impacts of Zero Gravity

By Emily Grenfell


It has long been a myth that Astronauts have their Appendix and Gall Bladders removed during preparatory surgery before space flight. While this is still considered for long duration space travel, like the forthcoming mission to Mars, it’s not current practice. Instead those in charge of space exploration trust in the unlikeliness of one of these conditions becoming chronic while an individual is in space.

So far, no astronaut has ever suffered from Appendicitis or Cholecystitis while in space, but astronauts do suffer from some very specific health problems while in zero gravity.


Lack of sleep

Sleep is a problem for astronauts. Stressful working conditions, challenges to health and body functions, coupled with sun rises and sunsets every 90 minutes, make for a challenging sleep environment. Some space missions see up to half the crew taking sleeping pills, and nearly half of all medication used in zero gravity is designed to help astronauts sleep. Despite this the average space traveller will get approximately two hours less sleep every night they spend in space.



The Earth’s atmosphere protects us from dangerous levels of radiation given of during solar storms. For Astronauts, increased exposure can lead to radiation sickness, cancer, and organ damage. Most of the dangerous radiation in space consists of electrically charged particles: high-speed electrons and protons from the Sun, and massive, positively charged atomic nuclei from distant supernovas. The ISS has radiation ‘safe zones’ and the crew are forewarned if a big radiation storm is coming.


Back ache

The problem may sound ordinary, but the cause is not. Removing gravity from the body has strange effects on our anatomy, and one of these is to decompress the spine. Vertebrae separate slightly and relaxation of back muscles and ligaments leads to back ache. Astronauts grow up to two inches taller while in space, but they always return to their natural height when they return to Earth.



Early astronauts during the Apollo missions reported seeing flashes or streaks of light that seemed to come from nowhere. During a mission on the International Space Station in 2012, Don Pettit described “flashes in my eyes, like luminous dancing fairies.” This may sound like the onset of cabin fever, but in reality these are caused by cosmic rays: free moving subatomic particles from distant destructing stars. Here on Earth the atmosphere absorbs most of these, but in space they cause nerve cells in the visual system to produce the “dancing fairy” effect.


Psychological Problems

Lack of sleep, living for months in a confined space floating inches from death hundreds of miles from home all bring a certain psychological strain to the job. In addition, studies are beginning to show that basic mental abilities like attention span, task switching, bodily co-ordination, and problem solving, all work less well in space. 

In what must have been a very tense episode for mission control the crew of Skylab 4 switched off their radio. Long hours and exhaustion had led to disagreements with the ground crew, so they spent the day relaxing and enjoying the view.


Moon Dust

Moon dust is extremely sharp-edged, and if inhailed can harm the heart and lungs, with effects ranging from inflammation to a heightened risk of cancer. It’s comparable to asbestos.

The dust can cause intense skin irritation and abrasions. It’s also capable of wearing through layers on a boot of Kevlar-like material. If lunar dust scratches the cornea of an astronaut’s eye the issue is especially serious.



Nausea due to motion sickness is by far the most common side-effect of space travel with 40-50% of astronauts experiencing it. The reason for this is simple: on Earth we know which way is up. Sensors in the inner ear feel the gravitational pull and tell us our orientation. In space there is no gravity, so while an astronaut can see a ceiling and a floor, their brains cannot register it.

Like seasickness, symptoms tend to subside within the first few days, and regular motion sickness medicine is equally effective in space.


Surgery in Space

No incident has yet led to surgery being performed in space, but that doesn’t mean it won’t. Films like Gravity take injury in space to the extreme, but in reality dealing with a minor bleeding wound would be challenging. With no gravity, droplets of blood would float away from the wound, obscuring vision, and may be inhaled, causing any crew member to choke.

Neurosurgeon James Burgess at Allegheny General Hospital in Pittsburgh came up with the idea of placing a transparent dome over a wound, filling it with a fluid like saline solution, creating pressure that could either slow or stop bleeding until a surgeon has the chance to seal the wound. Originally invented to prevent delicate tissues from drying out during brain and spinal surgery:

“The concept is applicable in any surgical situation – on Earth or in space.” Burgess.

Surgical instruments can be used within the dome, creating an environment in which a surgeon can work without being blinded by floating particles, and without exposing the wound to infection.