This Is How Much Radiation You'd Be Exposed to If You Visited the Moon

Researchers have measured radiation exposure on the moon's surface for the first time—and found it's about 200 times higher than what we experience on Earth.

For a study published in the journal Science Advances, scientists examined data collected by China's 2019 Chang'E 4 lander—which achieved the first ever soft landing on the moon's far side last year—in order to work out how much radiation humans on future lunar missions would be exposed to.

They found that the average daily radiation dose on the moon's surface is 1,369 microsieverts per day. This means that for any given amount of time you stood on the moon—say, six hours—you would receive 200 times more radiation than you would on the surface of Earth.

Likewise, you would receive five to 10 times more radiation standing on the moon for a given amount of time than you would being on a transatlantic flight for the same duration. The radiation exposure the scientists measured is also 2.6 times greater than what the crew of the International Space Station (ISS) experience.

"Because astronauts would be in space and on the moon much longer than the duration of a transatlantic flight, this is a potential health issue," Robert Wimmer-Schweingruber, the study's corresponding author from Christian-Albrechts-University in Germany told Newsweek.

The latest findings represent the first time that radiation levels have been actively measured at the lunar surface. While astronauts on the six Apollo missions that landed on the moon all carried dosemeters with them, these only measured the total radiation exposure for the entire mission to, on and back from the moon.

"Thus our measurement is special in that it provides the first measurement on the surface of the moon," Wimmer-Schweingruber said.

The results are significant given that space agencies from around the world are planning to send humans to the moon aboard future missions. NASA, for example, is aiming to land astronauts on the moon by 2024 and build a sustainable presence on the lunar surface as part of its Artemis program.

But mission operators must take into account the fact that extended stays on the moon could pose "substantial risks" to astronauts from space radiation, according to the study.

These radiation sources include galactic cosmic rays (high energy particles originating from the sun, outside of the solar system, and distant galaxies,) solar particle events (when particles emitted by the sun become accelerated) and gamma radiation (electromagnetic radiation of the shortest wavelength and highest energy).

Being exposed to galactic cosmic rays over long periods of time, for example, can lead to a variety of health problems, including cataracts, cancer and degenerative central nervous system diseases. Meanwhile, exposure to solar particle events without adequate protection may cause severe, immediate damage.

According to Wimmer-Schweingruber, the latest results have significant implications for future human exploration of the moon.

"If or when humans build a habitat on the surface of the moon they will need to include significant shielding [around 30 inches of lunar soil]. At this depth beneath the surface, radiation levels are significantly lower and astronauts could live there for extended periods of time. This would mean having some heavy construction machines on the moon," he said.

"The effect of the radiation on astronauts is a long-term one. It increases the risk of cancer. Should there be a big solar eruption or storm, then radiation levels can be much larger, so large that they can cause acute radiation illness."

Martin Barstow, a professor of astrophysics and space science at the University of Leicester in the U.K., who was not involved in the latest paper, told Newsweek the findings will help space agencies to protect astronauts on future missions to the moon.

"Given the renewed interest around the world in lunar exploration by humans and the NASA Artemis program, data like this is very important to understand better the risks for future human exploration," he said.

"We could have probably predicted the order of magnitude risk from our existing knowledge of the space radiation environment, which is quite mature, as the moon has no protecting magnetosphere to speak of. However, there is, in the end, no substitute for real in-situ measurements to bring the issues of long duration exploration into focus."

Barstow said that while the measured dose is only a factor 2-3 times above that experienced on the ISS, the radiation was recorded during a solar minimum—the period of least activity in the star's 11-cycle—so it is at the low end of what could potentially be experienced.

The data collected is also from the far side of the moon, which always faces away from Earth, and so might not be representative of the side that faces towards us, where most exploration has been focused to date, he said.