Two forms of radiation pose potential health risks to astronauts: a chronic low dose of galactic cosmic rays (GCRs) and the possibility of short-term exposures to the solar energetic particles (SEPs) associated with solar flares and coronal mass ejections.
The radiation on Mars is much harsher than on Earth for two reasons: Mars lacks a global magnetic field, and the Martian atmosphere is much thinner than Earth's, providing little shielding to the surface.
Dr. Don Hassler, a Southwest Research Institute program director and RAD principal investigator said that the RAD surface radiation data show an average GCR dose equivalent rate of 0.67 millisieverts per day from August 2012 to June 2013 on the Martian surface. Radiation dose is measured in units of sievert (Sv) or millisievert (1/1000 Sv).
He added that in comparison, RAD data show an average GCR dose equivalent rate of 1.8 millisieverts per day on the journey to Mars, when RAD measured the radiation inside the spaceship.
According to RAD data, most mission radiation exposure will be during outbound and return travel, when astronauts will be exposed to the radiation environment in interplanetary space, shielded only by the spacecraft itself.
The total dose during just the transit phases of a Mars mission would be approximately 0.66 Sv for a round trip with current propulsion systems and during similar solar activity. A 500-day mission on the surface would bring the total exposure to around 1 Sv.
The study has been published online in the journal Science.
--ANI (Posted on 10-12-2013)