Clever mathematicians in Canberra are working out how to keep fit astronauts even fitter when they land on Mars - and unfit rich tourists from collapsing when they go for a spin in space.
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The researchers have taken decades of health data from astronauts going back to the Apollo Missions to examine how weightlessness, perhaps over months, would affect the body.
"The purpose of our model is to predict, with great accuracy, whether an astronaut can safely arrive on Mars without fainting. We believe it's possible," one of the researchers, Emma Tucker, said.
"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.
"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 on the news 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."
Dr Tucker is working with the project head, Lex van Loon, from the ANU Medical School,
They simulated the effects of prolonged exposure to zero gravity on the cardiovascular system, and whether the human body can tolerate Mars' gravitational forces - which aren't as strong as on Earth - without fainting or worse when stepping out of a spacecraft.
The biggest worry was exposure to microgravity - near zero gravity - which, combined with exposure to sun radiation, could cause "fundamental" changes to the body, according to Dr van Loon.
"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," he said.
He said it was also important to know whether space tourists (some of whom might be very unhealthy) could survive their jaunts.
"With the rise of commercial space flight agencies like Space X and Blue Origin, there's more room for rich but not necessarily healthy people to go into space, so we want to use mathematical models to predict whether someone is fit to fly to Mars," he said.