Mars-bound pioneers will be exposed to radiation levels that could effectively retire astronauts under NASA’s current standards, scientists reported Thursday. The radiation astronauts would face on a round trip would be comparable to getting an abdominal CT scan “about once every five days,” Cary Zeitlin, principal scientist for the NASA-led Martian Radiation Environment Experiment, told CNN.The findings were published Thursday in the journal Science, based on data from a device called the Radiation Assessment Detector that took readings during Curiosity’s trip to Mars. The spacecraft was similar to one that would carry humans, and scientists were interested in measuring galactic cosmic rays and solar energetic particles on the trip.
Zeitlin and his colleagues found voyagers could be exposed to between 554 and 770 millisieverts of ionizing radiation during the trip, depending on the level of solar activity. By comparison, the typical American receives about 6.2 millisieverts a year from natural and man-made sources, including medical diagnostic procedures.
“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,” they wrote.
In terms of health effects of that exposure, there are a lot of unknowns, Zeitlin said. There’s no effective, practical shielding method that would block all of the high-energy particles from getting to the astronauts aboard a mission to Mars, he said. The problem can be mitigated, Zeitlin said, but not eliminated…
RAD has found radiation levels on the Martian surface to be comparable to those experienced by astronauts in low-Earth orbit. A person ambling around the Red Planet would receive an average dose of about 0.7 millisieverts per day, while astronauts aboard the International Space Station experience an average daily dose between 0.4 and 1.0 millisieverts, Hassler said.
RAD’s measurements show that Mars’ atmosphere — though just 1 percent as thick as that of Earth — provides a significant amount of protection from the fast-moving particles streaking through our galaxy. (Mars lacks a global magnetic field, which helps shield Earth further.)
The long deep-space journey to Mars is another matter. RAD was turned on for most of Curiosity’s eight-month cruise to the Red Planet, and its data show that any potential Mars explorers would likely get around 1.9 millisieverts per day during the flight.
“We can survive the Mars surface. The hard part is the cruise,” Hassler said.
RAD’s data are far from the full story of radiation on (or en route to) Mars, Hassler stressed. For example, solar storms can blast huge clouds of charged particles into space, affecting radiation levels significantly. Curiosity flew through a few such clouds during its cruise but has yet to experience one on the Red Planet surface.
Potential radiation doses will also change as solar activity waxes and wanes on its regular cycle. Galactic cosmic rays vary by a factor of two over the course of the sun’s 11-year activity cycle, Hassler said. …