Astronauts are exposed to 200 times more radiation on the moon than on the surface of the earth

According to news from September 30, Beijing time, scientists have estimated the radiation dose received by astronauts on the moon with a fairly accurate estimate, but this result may not be enough to prevent humans from landing on the moon again to explore .

Through a new study, we finally know what kind of radiation environment the future lunar rover will face. When astronauts bounce on the surface of the moon, they will absorb about 60 microsieverts of radiation per hour, which is 5 to 10 times higher than the radiation dose on a transatlantic airliner, and about the amount of radiation we receive on the surface of the earth. 200 times.

In other words, the long-term stay of astronauts 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 hindrance for future missions to the moon.

Pioneering results of advanced landers

Scientists have known for a long time that the radiation level on the moon is relatively high because there is no atmosphere or magnetic field as protection (fortunately, the earth has these two barriers to protect life from harmful radiation). However, studies over the years have shown that accurate lunar radiation values ​​are difficult to determine.

For example, when the Apollo astronauts of the National Aeronautics and Space Administration (NASA) boarded the moon between 1969 and 1972, the radiometer used recorded the total radiation dose accumulated during the mission, rather than the surface radiation level of the moon. Details. The new research gives scientists a more detailed understanding.

These data are provided by the German-made Lunar Lander Neutron and Dosimetry (Lunar Lander Neutron and Dosimetry, LND for short), and it is China’s Chang’e 4 moon landing mission that carried this instrument. In January 2019, Chang’e-4 achieved a soft landing on the unexplored back of the moon for the first time, making history.

Chang’e 4 is composed of a lunar rover named “Yutu 2″ and a lander. The two are still in operation. The LND is part of the lander’s scientific payload, and its location is partially protected. Earth shows the radiation situation in the spacesuit.”

LND data shows that high-energy charged particles like galactic cosmic rays (GCRs) account for about 75% of the total dose of 60 microsieverts per hour on the surface of the moon. These particles are accelerated by distant supernovae. Extremely high speed.

According to this new study published online on September 25 in the journal Science Advances, the galactic cosmic ray radiation on the moon is 2.6 times higher than that received by astronauts on the International Space Station (Space Station When operating over the earth’s atmosphere, it will be protected by the earth’s magnetic field).

Will not hinder the Artemis plan

The National Aeronautics and Space Administration (NASA) is committed to sending astronauts to the moon in 2024, and through the space exploration program called “Artemis” (Artemis), in this decade, establish a space on the moon and its surroundings. A space station for human sustainable existence. NASA officials said that the experience gained in the Artemis program will also help pave the way for manned landing on Mars, and according to NASA’s vision, manned landing on Mars will be realized in the 1930s.

An interpretation of NASA’s radiation exposure requirements shows that the latest reported data will not affect the Artemis project. NASA’s requirements stipulate that no occupational radiation dose received by any astronaut can increase the lifetime risk of cancer death by more than 3%. The total equivalent dose that causes this danger depends, among other factors, on the gender of the astronaut and the age when the radiation began.

Women and young astronauts face greater risks. For example, a female astronaut who started aerospace career at the age of 25 has an occupational exposure limit of 1 million microsieverts, while a male who started flying at the age of 55 has an occupational exposure limit four times this limit. However, at 60 microsieverts per hour, the 25-year-old female astronaut can spend nearly 700 days exploring the lunar surface before she exceeds her lifetime exposure limit (this calculation does not include her travel to and from the moon) time).

The authors of the study stated that the galactic cosmic-ray values ​​measured by the LND may be higher than any radiation exposure experienced by astronauts walking on the surface of the moon, because these data were collected during periods of inactivity during the 11-year active cycle of the sun, rather than In other words, more galactic cosmic rays can pass through the heliosphere, charged particle bubbles, and the magnetic field around the sun itself.

However, all this does not mean that in the Artemis program, the time limit for astronauts to land on the moon is only two years; for safety reasons, NASA undoubtedly hopes that the radiation exposure of astronauts will “flatten” over time. For example, for NASA astronauts flying on the International Space Station, their annual radiation cannot exceed 50,000 microsieverts.

On the other hand, NASA may also try to minimize the radiation risks experienced by the astronauts of the Artemis program, especially those who perform missions on the surface of the moon and orbit the moon.

“In longer missions to the moon, astronauts must protect themselves from (radiation exposure), and they can cover their habitat with a thick layer of lunar rock,” one of the study authors, Robert Kiel University, Germany Wimmer-Schweingruber (Robert Wimmer-Schweingruber) said, “This can reduce the risk of cancer and other diseases caused by living on the moon for a long time.” Wimmer-Schweingruber The team built LND.

These measures will also help prevent sporadic but potentially dangerous solar eruptions, so-called solar particle events (SPEs). In the coverage of this new study, LND did not find any solar proton events, but future lunar explorers are likely to encounter these energetic particles.

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