Radiation is one of the main dangers of space travel, and with renewed focus on sending human crews back to the Moon it’s important to understand the risks they face. Now we have the clearest data on that to date, thanks to a dedicated instrument onboard the Chinese lunar lander Chang’e-4.
Humans evolved to live on Earth, so we don’t fare too well as soon as you take us out of that environment. Low gravity can weaken muscles and bones, and beyond the protective bubble of our home planet’s magnetic field, radiation from the Sun and cosmic rays increase the risk of cancer, dementia and cardiovascular disease, among other things.
But exactly how much radiation would humans be exposed to on the Moon? Apollo astronauts carried instruments called dosimeters to measure that, but their exposure was measured over the entire trip. No direct detections have ever been conducted on the Moon until now.
When Chang’e-4 touched down on the far side of the Moon in January 2019, it was carrying the Lunar Lander Neutron and Dosimetry (LND) instrument with it. Researchers at Kiel University, the German Aerospace Center (DLR), and the Chinese Academy of Sciences have now reported the results of over a year of measurements from this instrument. The dosimeter was protected by about the same level of shielding as a spacesuit would offer a human, so the results should be fairly accurate, the team says.
The instrument recorded an equivalent dose rate of around 60 microsieverts per hour. That’s about 200 times higher than what we’re exposed to here on the ground, between five and 10 times more than you’d get on a long-haul flight, and about 2.6 times more than experienced by astronauts on the International Space Station.
There are ways to reduce that exposure though. Moon bases could be set up in huge caverns and lava tubes that are believed to sprawl underground, or shelters constructed of moon dust could provide adequate protection on the surface.
"We humans are not really made to withstand space radiation,” says Robert Wimmer-Schweingruber, second author of the study. “However, astronauts can and should shield themselves as far as possible during longer stays on the Moon, for example by covering their habitat with a thick layer of lunar soil.”
The team says that this more accurate reading can inform not just future crewed missions to the Moon, but also give a good starting point for better models of other planets like Mars.
The research was published in the journal Science Advances.
Source: University of Kiel
