VOA慢速英语--嫦娥四号测量表明月球上的辐射比地球上的多200倍（在线收听）

New measurements show that radiation levels on the moon are two to three times higher than on the International Space Station.

The measurements were taken by an instrument on China's Chang'e-4 lunar lander. The spacecraft touched down on the far side of the moon in January of 2019.

German and Chinese scientists involved in the experiment say the Chinese lander provided the first "active" measurements of radiation levels on the surface of the moon. The findings were recently reported in a study in the publication Science Advances.

The study comes as the United States and several other countries develop plans to send astronauts to explore the moon. The American space agency NASA has a goal of landing the first woman and next man on the moon by 2024 as part of its Artemis program. It also wants to set up a long-term base on the moon by 2028.

But space radiation presents major health risks to future astronauts. Cancer is the main health concern, but radiation exposure can also lead to other diseases.

NASA has already warned that space travelers spending long periods in places like the moon or Mars will face high levels of harmful radiation.

Earth's atmosphere and magnetic shield protect humans from the extreme radiation present in the universe. But astronauts aboard the International Space Station receive more than 10 times the radiation that we receive on Earth.

The new study suggests that radiation exposure on the moon would be 2.6 higher than on the International Space Station. The researchers said astronauts on the moon would get about 200 times more radiation than we experience on Earth.

Robert Wimmer-Schweingruber is an astrophysicist at the University of Kiel in Germany. He helped lead the research. He told the French press agency, AFP, the finding led his team to predict that astronauts would only be able to stay on the moon for about two months under current conditions.

"Humans are not really made for these radiation levels and should protect themselves when on the moon," Wimmer-Schweingruber said.

He added that radiation levels should be about the same in all areas of the moon, except for near the walls of deep craters. "Basically, the less you see of the sky, the better," he said.

The researchers suggested that astronauts could build shelters made of moon dirt for protection during stays of more than a few days. They said the shelters' walls would need to be about least 80 centimeters thick. A wall thicker than that, they said, could cause the dirt to give off its own secondary radiation. Such radiation is created when cosmic rays interact with the lunar soil.

NASA has said it will have radiation detectors and a safe shelter on all of its crew spacecraft flying to the moon.

Thomas Berger is a physicist with the German Space Agency's medicine institute. He also took part in the study. He called results of the experiment "immense." The method finally gives scientists a "data set" that can be used to effectively measure radiation and study its effects on humans, Berger said.

The radiation levels described in the study are similar to levels that models have already predicted. Kerry Lee is a space radiation expert at NASA's Johnson Space Center in Houston. Lee said the measurements "agree nearly exactly" with those made by a detector on a NASA orbiter that has been circling the moon for more than 10 years.

"It is nice to see confirmation of what we think, and that our understanding of how radiation interacts with the moon, is as expected," Lee said.

Words in This Story

exposure – n. coming in contact with something

shield – n. an object used to protect something

crater – n. a large round hole in the ground made by the explosion of a bomb or by something falling from the sky

cosmic ray – n. high-energy particles that move through space at nearly the speed of light

detector – n. a device that helps notice something that is hidden or unclear

immense – adj. extremely good

interact – v. to communicate with or react to