Recent data suggests astronauts travelling to Mars would receive more than the recommended lifetime dose of radiation and potentially raise their risk of cancer. Keeping astronauts safe from dangerous levels of radiation during travel to Mars in the coming years will prove to be difficult and require technological advances, but is not impossible.
The Curiosity rover, outfitted with the Radiation Assessment Detector (RAD), took measurements of the levels of radiation in the environment during a cruise to Mars last year in order to better understand the radiation exposure astronauts would sustain in a manned mission. The results were published in a recent edition of Science. While measurements of deep space radiation have previously been recorded, RAD was the first to record from within a protected spacecraft, much like what an astronaut would experience. While the high measurements of radiation penetration into the spacecraft were not unexpected given what is known about deep space, it is certainly sobering.
Carl Zeitlin, the lead author on the study, commented, "I would not call this a surprising result per se, but it does show with real data for the first time that people going to Mars will get a substantial dose of radiation from the transit leg alone.”
Time spent on the surface of Mars would likely add a significant amount of radiation exposure to the already high total. Measurements from the RAD's time spent on Mars is currently being analyzed by the same group of scientists.
There are two sources of radiation in deep space that pose a health risk to astronauts. The first is a chronic, low-dose exposure to galactic cosmic rays (GCRs), which tend to be highly energetic and are not stopped by the walls of the spacecraft, a process termed “shielding.” The second source of radiation is low-energy solar energy particles (SEPs), which are irregularly accelerated by events on the Sun. Shielding is more effective against the comparatively low energy SEPs versus the GCRs.
While the RAD device was shielded from radiation by variable mass distribution, a manned ship would likely be designed to contain a more even distribution of mass. It is also feasible that alternatives to this “passive” shielding may be explored. Passive shielding, like what was used to protect RAD, is essentially the blocking of radiation particles with materials such as aluminum or lead. Active shielding is another way of combating radiation, but by deflecting charged particles outside of a protected area by use of an electromagnetic field. However this is investigated, it is clear that improved shielding is a high priority for manned missions.
Equally important is shortening the duration of flights to Mars. Zeitlin notes that major advances in propulsion systems are necessary to reduce the exposure to radiation on outward-bound flights.
So what does this mean for MarsOne efforts to colonize Mars in the coming decades? The authors of this paper and others in the field maintain that the RAD data does not mean we are no longer headed to Mars. It’s merely a part of the data collection process to better prepare for this voyage.