The Apollo missions of the 1960s and 1970s was proved that it safe for astronauts to spend a few days on the surface of the Moon. But now, it has been found that the radiation can cause lasting health effects, from cataracts to cancer and neurodegenerative diseases. Actually, NASA did not take daily radiation measurements to help quantify the amount absorbed by human tissues. The measurement would help scientists to quantify just how long crews could stay on the lunar surface. However, this problem is now resolved through an experiment, carried out by China’s Chang’E 4 lander in 2019 the result of which were published by a Chinese-German team is the formal Science advances on September 25, 2020.
As per the report, the radiation exposure on the Moon is 1,369 microsieverts (mSv) per day, which is about 2.6 times higher than the International Space Station crew’s daily exposure level. The radiation levels on Moon are about 200 times higher than on the surface of the Earth and five to 10 times higher than on a flight from New York to Frankfurt. Therefore, one can stay there for approximately two months after considering the radiation exposure from the roughly week-long journey there, and week back. To measure the exposure, there are several sources of radiation exposure, such as galactic cosmic rays, sporadic solar particle events, and neutrons and gamma rays from interactions between space radiation and the lunar soil.
The ISS is still partly shielded by the Earth’s protective magnetic bubble, called the magnetosphere, which deflects most radiation from space. Since the Earth’s atmosphere provides additional protection for humans on the surface, one is more exposed to the radiation the higher up one goes.
NASA plans to bring humans to the Moon by 2024 under the Artemis mission for a long-term presence, which would include astronauts working and living there. As per co-author Wimmer-Schweingruber, we will have to build habitats, shielded from radiation, coated with 80 centimetres of lunar soil, if humans are made to spend more than two or three months on the lunar surface.
More Information:
Sievert (Sv) is a unit of radiation absorption in the International System of Units (SI). It takes into account the relative biological effectiveness (RBE) of ionising radiation like X rays, gamma rays, neutrons, etc. because each form of the radiation has a slightly different effect on living tissue. So, one sievert is generally defined as the amount of radiation roughly equivalent in biological effectiveness to one gamma radiation or gray. Since the sievert is inconveniently large for various applications, the millisievert (mSv) is frequently used in its place and it is equal to 1/1,000 sievert.
Courtesy: barrons.com, britannica.com, nasa.gov