Using the Lunar Lander Neutrons and Dosimetry (LND) experiment aboard China’s Chang’E 4 lander, a team of researchers from Germany and China has measured an average dose equivalent of 1,369 μSv/day on the surface of the Moon.
The Moon is the next stepping stone for human space exploration, and several nations have announced plans for its exploration by humans.
Space radiation exposure is one of the major risks for astronauts’ health as the chronic exposure to galactic cosmic rays may have late health effects such as induction of cataract, cancer, or degenerative diseases of the central nervous system or other organ systems.
It appears that there have been no active measurements of the radiation dose rate on the lunar surface until China’s Chang’E 4 mission landed in the von Karman crater on the far side of the Moon in January 2019.
During the Apollo missions, astronauts carried dosimeters with them to the Moon, but the radiation data from the surface of the Moon were never reported.
“Over the coming years and decades, various nations are planning to send crewed missions to explore the Moon. Space radiation poses a significant risk to the health of humans,” said LND project manager Dr. Oliver Angerer, a researcher in the Space Administration at the German Aerospace Center (DLR).
“The Apollo astronauts carried radiation measuring devices, referred to as dosimeters, on their bodies. But these only determined the radiation exposure over the course of the entire mission.”
“The radiation exposure we have measured is a good benchmark for the radiation within an astronaut suit,” added co-author Dr. Thomas Berger, a researcher at the German Aerospace Center (DLR).
The LND instrument measured an average dose equivalent of 1,369 μSv/day on the lunar surface.
For the same time period, the dose equivalent onboard the International Space Station (ISS) was 731 μSv/day with contributions only from galactic cosmic rays of 523 μSv/day. The additional 208 μSv/day is due to protons while crossing the South Atlantic Anomaly.
Therefore, the daily galactic cosmic ray dose equivalent on the surface of the Moon is around a factor of 2.6 higher than the dose inside the ISS.
“The measurements show an equivalent dose rate of about 60 μSv per hour,” said co-author Dr. Robert Wimmer-Schweingruber, a scientist at Kiel University.
“In comparison, on a long-haul flight from Frankfurt to New York, it is about 5 to 10 times lower, and on the ground well over 200 times lower.”
“Since astronauts would be on the Moon for much longer than passengers flying to New York and back, this represents considerable exposure for humans.”
“During long-term stays on the Moon, the astronauts’ risk of getting cancer and other diseases could thus be reduced,” said DLR researcher Dr. Christine Hellweg, co-author of the study.
References: Shenyi Zhang et al. 2020. First measurements of the radiation dose on the lunar surface. Science Advances 6 (39): eaaz1334; doi: 10.1126/sciadv.aaz1334 link: https://advances.sciencemag.org/content/6/39/eaaz1334