NASA's Curiosity proves astronauts on a Mars mission would get a big dose of damaging radiation

Astronauts heading to Mars would face exposure to a deluge of radiation, in some cases as much as NASA policy permits, according to new data from the Curiosity rover. The space agency limits astronauts to a 3% increased risk of fatal cancer. This translates to different levels of radiation exposure, depending on an astronaut's age and gender.

According to a paper published in Friday's edition of the journal Science, radiation exposure in a nonstop round-trip to Mars, which would take about a year, would ring in at about 662 millisieverts.

One sievert, or 1,000 millisieverts, of radiation over time is generally associated with a 5% increase in fatal cancer risk.
"It is clear that the exposure from the cruise phases alone is a large fraction of (and in some cases greater than) currently accepted astronaut career limits," the authors wrote.

As the Obama administration calls for a manned trip to the Red Planet by the mid-2030s, mission planners will have to address the challenge, experts said.

"It's not a show-stopper," said Lewis Dartnell, an astrobiologist at the University of Leicester in England who was not involved in the work. "But it does mean if we want to do a human mission to Mars as safely as we can, we perhaps need to start thinking about how to better shield and protect these astronauts against radiation in space."

Curiosity's RAD instrument was designed to measure the radiation on the surface of Mars. But late in the game, scientists realized they could also use it in flight to test how much radiation got through the vessel's shielding.

Over the 348 million miles Curiosity traveled to Mars, the rover only experienced five solar energetic particle events, which lasted up to a few days. Though levels of radiation shot up during those events, overall they contributed only about 5% of the total radiation exposure during the trip.