The moon is constantly bombarded by cosmic radiation and, unlike the Earth which has a magnetic field to keep it safe, there is no protection on the lunar surface from these potentially dangerous particles.
Now, a study has measured the levels of radiation on the moon for the first time and found they are 200 times the levels here on Earth. However, experts say that the levels are still safe for long-term exploration of the moon.
The new study used data from China’s Chang’e 4 lander which has been exploring the far side of the moon. It took measurements with an instrument called a dosimeter which measures both charged and neutral particles on the moon’s surface. It is the charged particles that are dangerous to humans and can have short-term effects like nausea and vomiting and can cause long-term health problems like increased rates of cancer.
The study found that, even though the levels of radiation are much higher on the moon than on Earth, they are only around five to 10 times the levels that a passenger experiences on an intercontinental plane flight. Radiation exposure is still a health concern, but this exposure should be manageable through steps like constructing a lunar base covered in at least 50 centimeters of lunar soil. That should protect astronauts most of the time, and a special shielded chamber inside could protect them from rare but dangerous radiation flare-ups.
A key requirement for NASA is that astronauts’ risk of cancer should not be raised by more than 3%, and these radiation levels stay below that threshold.
While the exposure of lunar astronauts to radiation has been measured before during the Apollo missions, these measurements were taken over their journey from Earth, through space, on the moon, and back again. The actual level of radiation exposure on the moon’s surface had only been estimated “from extrapolation and modeling,” physicist Robert Wimmer-Schweingruber of the University of Kiel, a co-author of the study, said in Science. “We’ve never actually measured them exclusively on the moon.”
NASA is currently planning a return mission to the moon in 2024 under the Artemis program, and wants to eventually set up a long-term base there. Experts say that while radiation still needs to be considered and accounted for when planning lunar missions, if astronauts have a properly shielded base then they should be able to live on the moon for up to six months without exceeding NASA’s safety limits.