Scientists have made a fairly accurate estimate of the radiation dose to astronauts on the moon, but this result may not be enough to prevent humans from landing on the moon again. Through a new study, we finally know what kind of radiation environment will be faced by future moon walkers. As astronauts hop around the surface of the moon, they will absorb about 60 microsevers of radiation per hour, which is five to ten times higher than that on a transatlantic airliner, and about 200 times the radiation dose we receive on the earth’s surface. < / P > < p > in other words, astronauts’ long stay on the moon will expose their bodies to high doses of radiation. Although these values are indeed high, they may not be enough to be a major obstacle for future missions to the moon. < / P > < p > scientists have long known that the level of radiation on the moon is relatively high because there is no atmosphere or magnetic field to protect it (fortunately, the earth has these two barriers that protect life from harmful radiation). Over the years, precise numerical studies have shown that lunar radiation is difficult to determine. For example, when Apollo astronauts of NASA landed on the moon between 1969 and 1972, the radiometer used to record the total radiation dose accumulated during the mission, rather than the details of the radiation level on the surface of the moon. The new research gives scientists a more detailed understanding. < / P > < p > these data are provided by the lunar lander neutron and dosimetry (LND) made in Germany, and it is China’s chang’e-4 lunar landing mission that carries these data. In January 2019, chang’e-4 made history by making a soft landing on the undetected back of the moon for the first time. < p > < p > chang’e-4 is composed of a lunar rover named “Yutu 2” and a lander, both of which are still in operation. LND is part of the scientific payload of the lander, and its position has been partially protected, which can “show the radiation situation in the spacesuit very well”. < p > < p > LND data show that high-energy charged particles such as galactic cosmic rays (GCRs) account for about 75% of the total dose of 60 microsevers per hour on the lunar surface, and these particles are accelerated to extremely high speed by distant supernova explosions. < / P > < p > according to the new study, published online September 25 in the journal science advances, galactic cosmic ray radiation on the moon is 2.6 times higher than that received by astronauts on the international space station (the station is protected by the earth’s magnetic field when it is operating over the earth’s atmosphere). < / P > < p > NASA is committed to sending astronauts to the moon in 2024 and, through the space exploration program called Artemis, will build a sustainable space station for human beings in and around the moon within this decade. NASA officials say the experience gained in the Artemis Project will also help pave the way for a manned landing on Mars, which NASA envisions to be achieved in the 1930s. < / P > < p > An Interpretation of NASA’s radiation exposure requirements shows that the latest reported data will not affect the Artemis program. According to NASA’s requirements, no occupational radiation dose received by any astronaut can increase his or her lifetime risk of cancer death by more than 3%. The total equivalent dose that causes this risk depends, among other things, on the sex of the astronauts and the age at which they begin to receive radiation. < / P > < p > women and young astronauts are at greater risk. For example, the occupational exposure limit for a female astronaut who started her career in space at the age of 25 is 1 million microsevers, while that for a man who started flying at the age of 55 is four times that. However, at 60 microsevers per hour, the 25-year-old female astronaut can spend nearly 700 days exploring the surface of the moon to exceed her life exposure limit (which does not include her time to and from the moon). < / P > < p > the authors of the study said that the galactic cosmic ray values measured by LND may be higher than any radiation exposure experienced by astronauts walking on the surface of the moon, because these data are collected during the inactive period of the sun’s 11 year active cycle, and relatively more galactic cosmic rays can pass through the heliosphere, charged particle bubbles and the magnetic field around the sun itself. < / P > < p > however, all this does not mean that the time limit for astronauts to land on the moon in the Artemis Project is only two years; for the sake of safety, NASA undoubtedly hopes that the radiation exposure of astronauts will “flatten out” over time. For example, for NASA astronauts flying on the international space station, the annual radiation dose should not exceed 50000 microsevers. < / P > < p > on the other hand, NASA may also try its best to minimize the radiation risk experienced by the Artemis program astronauts, especially those on missions and around the moon. < / P > < p > “on longer missions to the moon, astronauts have to protect themselves from (radiation exposure), and they can cover their habitat with a thick layer of lunar rock,” said Robert Weinger of Kiel University in Germany, one of the study authors “This can reduce the risk of cancer and other diseases associated with prolonged life on the moon,” Wimmer Schweingruber said Wilmer Schweingruber’s team built LND. These measures will also help prevent sporadic but potentially dangerous solar eruptions, known as solar particle events (SPEs). In the coverage of this new study, LND has not found any solar proton events, but future lunar explorers are likely to encounter these high-energy particles. Didi Qingju bicycle has entered 150 cities