Astronomers now say the moon is eating up molecules from Earth’s atmosphere

Particles from Earth’s atmosphere have been carried into space by solar wind and have been landing on the moon for billions of years, mixing into the lunar soil, according to a new study.

The research sheds new light on a puzzle that has endured for over half a century since the Apollo missions brought back lunar samples with traces of substances such as water, carbon dioxide, helium and nitrogen embedded in the regolith — the moon’s dusty surface layer.

Early studies theorized that the sun was the source of some of these substances. But in 2005 researchers at the University of Tokyo suggested that they could have also originated from the atmosphere of a young Earth before it developed a magnetic field about 3.7 billion years ago. The authors suspected that the magnetic field, once in place, would have stopped the stream by trapping the particles and making it difficult or impossible for them to escape into space.

Now, the new research upends that assumption by suggesting that Earth’s magnetic field might have helped, rather than blocked, the transfer of atmospheric particles to the moon — which continues to this day.

“This means that the Earth has been supplying volatile gases like oxygen and nitrogen to the lunar soil over all this time,” said Eric Blackman, coauthor of the new study and a professor in the department of physics and astronomy at the University of Rochester in New York.

“It has long been thought that the Moon initially formed from an asteroid impact to the proto-Earth, during which there was a lot of initial mixing of such volatiles from Earth to moon,” he added via email. “Our results show that there is still volatile sharing, even over billions of years.”

The presence of useful elements such as oxygen and hydrogen on the moon’s surface could be of interest for lunar exploration.