As the United States prepares to bring humans back 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 and neurodegenerative diseases.
Although the Apollo missions of the 1960s and 1970s proved it was safe for people to spend a few days on the lunar surface, NASA did not make daily radiation measurements that would help scientists quantify how long crews could stay.
This question was answered on Friday after a Chinese-German team posted in the magazine Advances in science the results of an experiment conducted by the Chinese lander Chang’E 4 in 2019.
“So this limits your stay to about two months on the surface of the moon,” he added, once he took into account the radiation exposure of the trip about a week and a week back.
There are several sources of radiation exposure: galactic cosmic rays, sporadic solar particle events (e.g. from solar flares) and neutrons and gamma rays from interactions between space radiation and the lunar soil.
The 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, about 2.6 times 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 the higher we go we are more exposed.
“The radiation levels we measured on the moon are about 200 times higher than those on the surface of the Earth and five to 10 times higher than those of a flight from New York to Frankfurt,” added Wimmer-Schweingruber.
NASA is planning to get humans to the moon by 2024 as part of the Artemis mission and said it has plans for a long-term presence that would include astronauts working and living on the surface.
For Wimmer-Schweingruber, there is a solution if we want humans to spend more than two or three months: build radiation-protected habitats by coating them with 80 centimeters (30 inches) of lunar soil.
© Agence France-Presse