The results weren't good.
In typical politio-speak, NASA reported "The findings … indicate radiation exposure for human explorers could exceed NASA's career limit for astronauts if current propulsion systems are used."
That's code for, "a mission to Mars will seriously curtail your life expectancy."
This writer (who is old enough!) recalls the worry surrounding the level of radiation to be experienced by the Apollo astronauts to the Moon, with a maximum time outside of the Earth's protective features never exceeded 10 days. A mission to Mars will be multiple years.
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Of some interest was the claim that many of the Apollo astronauts reported bright streaks in their vision. These were attributed to cosmic rays passing through their eyes (or perhaps the visual cortexes of their brains).
The Mars Science Laboratory's Radiation Assessment Detector (RAD) was the first attempt to measure interplanetary radiation from inside a craft that offered similar protection to existing manned craft.
"As this nation strives to reach an asteroid and Mars in our lifetimes, we're working to solve every puzzle nature poses to keep astronauts safe so they can explore the unknown and return home," said William Gerstenmaier, NASA's associate administrator for human exploration and operations in Washington, D.C. "We learn more about the human body's ability to adapt to space every day aboard the International Space Station. As we build the Orion spacecraft and Space Launch System rocket to carry and shelter us in deep space, we'll continue to make the advances we need in life sciences to reduce risks for our explorers. Curiosity's RAD instrument is giving us critical data we need so that we humans, like the rover, can dare mighty things to reach the Red Planet."
There are two primary sources of radiation that would be experienced by our intrepid Mars-exploring wannabe. Firstly, we have the long-travelled emissions from Supernova (and similar) events throughout the universe. These are known as galactic cosmic rays (GCRs). The other source is solar energetic particles (SEPs) which are associated with solar flares and coronal mass ejections from the Sun.
NASA is good at protecting Astronauts from SEPs, but very poor at GCRs. In addition, it is easy to detect SEP events and keep the astronauts in the best-protected parts of a spacecraft while the SEPs pass. That is not possible for the much higher-energy GCRs, which will pass effortlessly through any shielding likely to be included on an interplanetary craft.
According to the report, Radiation exposure is measured in units of Sievert (Sv) or milliSievert. Long-term population studies have shown exposure to radiation increases a person's lifetime cancer risk. Exposure to a dose of 1 Sv, accumulated over time, is associated with a 5 percent increase in risk for developing fatal cancer.
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"In terms of accumulated dose, it's like getting a whole-body CT scan once every five or six days," said Cary Zeitlin from the Southwest Research Institute (SwRI) in San Antonio, Texas. "Understanding the radiation environment inside a spacecraft carrying humans to Mars or other deep-space destinations is critical for planning future crewed missions."
Once the Curiosity rover landed on the surface, the RAD continued to operate, giving NASA's scientists plenty more information on the level of protection that will be required in order to safely venture out on the surface of the red planet. This information will help guide planning for possible missions in the future.
