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French Media AgencySeptember 28, 2020 10:50:29 am
As the United States prepares to return humans to the Moon this decade, one of the biggest dangers future astronauts will face is space radiation that can cause lasting health effects, from cataracts to cancer to neurodegenerative diseases.
Although the Apollo missions of the 1960s and 1970s showed that it was safe for people to spend a few days on the lunar surface, NASA did not take daily radiation measurements that would help scientists quantify how long crews could stay.
This issue was resolved on Friday after a Chinese-German team published in the magazine Scientific advances the results of a experiment conducted by China’s Chang’E 4 lander in 2019.
“The radiation from the Moon is two to three times greater than that on the ISS (International Space Station),” co-author Robert Wimmer-Schweingruber, an astrophysicist at the University of Kiel, told AFP.
“So that limits their stay to about two months on the surface of the Moon,” he added, once radiation exposure from the trip of about a week there and the week before is taken into account.
There are several sources of radiation exposure: galactic cosmic rays, sporadic solar particle events (eg, from solar flares), and neutrons and gamma rays from interactions between space radiation and the lunar soil.
Scientist-astronaut Harrison Schmitt collecting moon rake samples during the first Apollo 17. Schmitt was the lunar module pilot for the mission. The moon rake is used to collect discrete rock samples and rock fragments of varying sizes. Image courtesy: NASA
Radiation is measured using the sievert unit, which quantifies the amount absorbed by human tissues.
The team found that radiation exposure on the Moon is 1,369 microsieverts per day, roughly 2.6 times higher than the daily dose of the International Space Station crew.
The reason for this is that the ISS is still partially shielded by Earth’s protective magnetic bubble, called the magnetosphere, which deflects most of the radiation from space.
Earth’s atmosphere provides additional protection for humans on the surface, but we are more exposed the higher we go.
“The radiation levels we measure on the Moon are roughly 200 times higher than on the Earth’s surface and five to 10 times higher than on a flight from New York to Frankfurt,” added Wimmer-Schweingruber.
NASA plans to get humans to the Moon by 2024 under the Artemis mission and has said it has plans for a long-term presence that would include astronauts working and living on the surface.
For Wimmer-Schweingruber, there is an alternative solution if we want humans to spend more than two or three months: build habitats that are protected from radiation by covering them with 80 centimeters (30 inches) of lunar soil.
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