The 12 human beings who have walked on the moon were all bombarded by radiation roughly 200 times what we experience here on Earth, reports Adam Mann for Science. That’s two to three times what astronauts experience aboard the International Space Station, explains Marcia Dunn for the Associated Press (AP), suggesting that any long term human presence on the moon will require shelters with thick walls capable of blocking the radiation.
Despite the fact that the measurements, which come courtesy of China’s Chang’e-4 lunar lander, are quite high compared to what we experience on Earth, the data is quite useful for protecting future moonwalkers. According to Science, the levels of radiation at the lunar surface wouldn’t be expected to increase the risk of NASA astronauts developing cancer by more than 3 percent—a risk threshold the agency is legally required to keep its astronauts’ activities safely below.
“This is an immense achievement in the sense that now we have a data set which we can use to benchmark our radiation” and to assess the risk posed to humans on the moon, Thomas Berger, a physicist with the German Space Agency’s medicine institute, tells the AP.
Some forms of radiation, which is electromagnetic energy emitted in forms like heat, visible light, X-rays and radio waves, can mess with the cells inside the human body by breaking up the atoms and molecules they’re made of. On Earth, most people are familiar with ultraviolet radiation’s harmful effects on our skin, but in space, astronauts are also subjected to galactic cosmic rays, accelerated solar particles, neutrons and gamma rays, according to the research published this week in the journal Science Advances. This material can damage our DNA and lead to increased incidences of cancer or contribute to other health problems such as cataracts and degenerative diseases of the central nervous system or other organ systems.
Humanity measured the radiation astronauts on the Apollo missions experienced on their journeys to the moon, but those measurements were cumulative for each astronaut’s entire journey, per Science. To figure out the daily dose of radiation exclusively on the surface of the moon, the robotic Chang’e-4 lander used a stack of ten silicon solid-state detectors.
The renewed interest in collecting such measurements is partly because NASA has plans to send more people to the moon. The Artemis moon mission, scheduled for 2024, will feature the first woman ever to walk on the moon as well as a week-long expedition to the lunar surface and a minimum of two moonwalks, reports Katie Hunt for CNN.
Berger tells the AP that these new findings suggest the shelters needed to protect Artemis’ astronauts during such a long stay on the moon should have walls made of moon dirt that are some two and a half feet thick. Science notes that the shelter would also need an even more heavily shielded inner sanctum to protect astronauts in the event of a solar storm. Adequate shielding for this inner chamber would be roughly 30 feet of water, and would also need to be reachable within 30 minutes—the current limit of satellites’ abilities to provide astronauts with advanced warning of such hazards.
The findings aren't exactly suprising: they are in line with calculations made using existing measurements. But they’re a crucial step towards putting people on the surface of the moon for extended periods of time. According to Science, the results confirm that with proper shielding astronauts could spend as long as six months on the moon.