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Another hitch on the way to Mars: too much radiation

Figuring out how to send humans to Mars was never going to be easy.

And research released today by scientists involved in the Curiosity rover mission gives new insight into one particularly dangerous hurdle: excessive radiation exposure.

An instrument aboard the spacecraft that delivered Curiosity measured 1.8 milliSieverts of radiation exposure for every day of the 253 day trip to Mars, according to a study that will be published in the journal Science tomorrow. (Radiation dose is measured in Sieverts.)

That translates to .66 Sieverts of exposure for a round trip. In humans, exposure to a dose of 1 Sievert of radiation is associated with a 5 per cent increase in fatal cancer risk. 

In other words, travelling to Mars is the equivalent of getting a full-body CT scan every five or six days, the researchers pointed out -- and that doesn't include the stay on the planet itself.

The Southwest Research Institute-led team designed the Radiation Assessment Detector (RAD) to measure radiation levels on the surface of Mars, they told media during a teleconference Thursday. But they realized it would be just as good at measuring the levels on the way there.

RAD, which is about the size of a coffee maker, is measuring two things: radiation from galactic cosmic rays, which is omnipresent in outerspace, and radiation from solar energetic particles from the sun, which are associated with solar flares and other intermittent events. Both are very energetic, and penetrate the walls of a spacecraft easily. 

Scientists who authored the study say that new efforts to shield astronauts are underway, including packing spacecraft walls with water and food. Cutting down on travel times enough -- to around 180 days -- could potentially require nuclear-thermal rockets, a technology years away. 

NASA astronauts have strict limits on their lifetime radiation exposure as a result of space travel -- they are only permitted a three per cent increased fatal cancer risk.

Whether its ethical to send humans to mars decades from now if the technology is there otherwise but the radiation exposure problem isn't solved is a question beyond this particular scientific study, the researchers said. 

Kate Allen is the Star's science and technology reporter. Find her on Twitter at @katecallen.



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