Washington (AFP)

The Chinese probe which landed in 2019 has allowed to answer a question left aside by the Apollo missions: the exact level of radiation on the Moon, an essential data when NASA wants to send astronauts there this decade for prolonged periods .

A team of Chinese and German researchers published Friday in the journal Science Advances the results of the experiment conducted by the Chang'e-4 lander, which recorded the radiation received on the surface every day.

Result: their level is 2.6 times higher than that received by the inhabitants of the International Space Station (ISS).

"The radiation on the Moon is between two and three times stronger than on the ISS," Robert Wimmer-Schweingruber, astrophysicist at the University of Kiel and co-author of the study, told AFP.

"This limits the length of stay on the Moon to about two months," he said conservatively, adding that this took into account the week of travel between Earth and the Moon and back.

Rays, cosmic and solar, can cause long-term damage at certain doses ranging from cancer to cataracts and neurodegenerative diseases.

The measurement is made with the sievert unit, which quantifies the radiation absorbed by human tissue.

On the Moon, the radiation is 1.369 microsievert per day, or 2.6 times the daily dose aboard the ISS, where crews typically stay six months but a few have stayed a year or more.

There is less radiation inside the station because it is partially shielded from cosmic rays by the Earth's magnetosphere.

On Earth, we are even more protected by the atmosphere, but this protection decreases with altitude.

"The level of radiation measured on the Moon is about 200 times higher than that observed on Earth, and 5 to 10 times higher than that of a flight between New York and Frankfurt," adds Robert Wimmer-Schweingruber.

NASA wants to return to the Moon in 2024 for the first time since 1972, and then build an infrastructure to send astronauts there regularly, such as a dress rehearsal for sending the first human to Mars.

For a period longer than two months on the Moon, Professor Wimmer-Schweingruber suggests building habitats protected from radiation by an 80-centimeter-thick covering of lunar soil.

© 2020 AFP