During the Curiosity rover's nine-month trip to Mars, it copped its fair share of radiation-producing solar flare and particle events. This, in turn, provided NASA with a fair chunk of information to help it figure out the protective requirements for humans to make the trip. Until now, the organisation didn't have radiation numbers from the perspective of being on the surface itself, but Curiosity has again delivered and the prospects look good, at least for now.
According Don Hassler, the principal investigator for Curiosity's "Radiation Assessment Detector" (with the appropriate acronym RAD), astronauts could "absolutely" live in the Martian environment without fear of overexposure. The statement was made at a press conference last week and covered by CNN's Light Years blog, which goes into a bit more detail on the specifics.
Firstly, Mars doesn't benefit from a magnetic field like Earth's, so that's one less defence against solar radiation. Complicating things is the fact Mars' atmosphere is only one percent as thick as ours. Even with these deficiencies, astronauts would be more worried about radiation exposure to and from the planet, rather than what they'd receive just walking around on the surface. The CNN story notes that astronauts would have to spend at least six months on Mars between jaunts to stay within "career limits".
NASA will have a better idea of the situation once Curiosity is exposed to a solar event, which it currently has yet to experience since landing back in August. These spikes will provide a clearer indication of humanity's chances at long-term Martian living arrangements, unless someone invents deflector shields in the meantime and renders it a moot point.
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