Updated 02 June 2018

5 changes to the human body when in outer space

It's a completely different environment, with forces unfamiliar to the human body. So, what are a few of the changes human bodies can expect when venturing into outer space?

When it comes to space travel, South Africans, or the country itself, don't really come to mind, like NASA for example. 

But things are changing, especially with Mark Shuttleworth circa 2002, Adriana Marais as a Mars One finalist, Elon Musk making massive strides with his company SpaceX, and the country getting its very own National Space Agency.

The Mars One mission, to determine whether humans will be able to inhabit another planet, is a major operation, requiring enormous amounts of preparation.

Researchers, scientists, physicists, doctors and advisors will look to past space missions and research to prepare them as well as they can for the journey ahead.

We still don't know everything about what happens to the human body when it enters an environment different to earth. We learned a lot when Mark Shuttleworth travelled into the great unknown, but our knowledge is not nearly complete:

  • Gravity: Many people don't realise that gravity holds body fluids, like blood, down when we're on earth. In space however, microgravity – close to zero gravity – causes fluids to rise from the bottom half of the body to the top.
  • Increase in height: You may think you suddenly started growing again once you leave the earth's atmosphere. Sorry to burst your bubble, but microgravity is the reason you are taller in space. Gravity causes the human spine to be compressed, but when in space, the spine becomes decompressed. Once astronauts return to earth, they return to their normal height.
  • Weakened muscles: Being weightless may sound like fun, but not for your muscles. Human muscles lose their definition and shrink in space. Astronauts are obliged to train every day.
  • Higher risk of cancer: Astronauts may be exposed to much more radiation when they're in space because they don't have the earth's magnetic field to protect them.
  • Genetic codes behave differently: We all have a certain genetic code that behaves a certain way when we're on earth. When in space, it seems to be a different scenario. A study was conducted on a set of identical twins, astronauts Mark and Scott Kelly. The National Aeronautics and Space Administration (NASA) sent Scott Kelly to space for just under a year and kept his twin, Mark, on earth. They did this to determine the long-term effects of living in space for longer periods of time on the human body. NASA confirmed their preliminary findings towards the end of January and gave another update mid-March. Mark and Scott are identical twins, and Scott's DNA didn't "fundamentally change", but researchers did see changes in his gene expression caused by his body's reaction to the different environment.