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There will be all sorts of challenges faced by astronauts headed into space and one day, perhaps relatively soon, to Mars. Among the challenges will be the effects of solar radiation and of weightlessness on the human body.

Our bodies are not accustomed to such an environment says Dr. Lex van Loon of the Australian National University (ANU) Medical School in this SpaceRef article.

“We know it takes about six to seven months to travel to Mars and this could cause the structure of your blood vessels or the strength of your heart to change due to the weightlessness experienced as a result of zero gravity space travel.”

Colleague Dr. Emma Tucker, astrophysicist and emergency medicine registrar, notes the human heart isn’t accustomed to the low or non-existent gravity environment of space or on another planet such as Mars. 
It therefore doesn’t have to work as hard pumping blood through our body and becomes lazy–with serious consequences if not anticipated and addressed.

“When you’re on Earth, gravity is pulling fluid to the bottom half of our body, which is why some people find their legs begin to swell up toward the end of the day. But when you go into space that gravitational pull disappears, which means the fluid shifts to the top half of your body and that triggers a response that fools the body into thinking there’s too much fluid,” says Tucker. “As a result, you start going to the toilet a lot, you start getting rid of extra fluid, you don’t feel thirsty and you don’t drink as much, which means you become dehydrated in space. This is why you might see astronauts…. faint when they step foot on Earth again. This is quite a common occurrence as a result of space travel, and the longer you’re in space the more likely you are to collapse when you return to gravity.”

All this makes being able to assess in advance a person’s ability to tolerate the challenges and effects of low gravity faced during space travel essential. 

After all, there are no hospitals close by when in space to render help if an astronaut gets into medical trouble. 

Assessing how different space travelers will respond to the environment of space is what a new mathematical model developed at ANU is designed to do–and it’s discussed in this article.