New findings suggest that Earth's magnetic field has played a surprising role in transporting particles from our atmosphere to the moon over vast stretches of time.

At first glance, the moon appears lifeless and inert. But its surface may tell a more complex story. For billions of years, tiny fragments of Earth's atmosphere have likely been arriving on the moon and becoming embedded in its soil. These materials may include substances that could one day help support human activity on the lunar surface. Until recently, however, scientists were unsure how these particles could travel such enormous distances or how long the process had been underway.

Researchers at the University of Rochester now report that Earth's magnetic field may assist rather than prevent this transfer. Their study, published in Nature Communications Earth and Environment, shows that atmospheric particles lifted by the solar wind can be guided outward along Earth's magnetic field. Since this magnetic shield has existed for billions of years, it could have enabled a slow but continuous movement of material from Earth to the moon across deep time.

"By combining data from particles preserved in lunar soil with computational modeling of how solar wind interacts with Earth's atmosphere, we can trace the history of Earth's atmosphere and its magnetic field," says Eric Blackman, a professor in the Department of Physics and Astronomy and a distinguished scientist at URochester's Laboratory for Laser Energetics (LLE).

These results suggest that lunar soil may preserve a long-running archive of Earth's atmosphere. They also raise the possibility that the moon contains resources that could prove valuable for astronauts living and working there in the future.

What Apollo Samples Revealed

Moon rocks and soil collected during the Apollo missions in the 1970s have been central to this research. Analyses of these samples show that the moon's surface layer, known as regolith, contains volatile substances such as water, carbon dioxide, helium, argon, and nitrogen. Some of these materials clearly come from the solar wind, the steady flow of charged particles streaming from the sun. However, the quantities found, particularly nitrogen, are too large to be explained by solar wind alone.

In 2005, scientists from the University of Tokyo proposed that part of these volatiles originated in Earth's atmosphere. They argued that this transfer could only have occurred early in Earth's history, before the planet developed a magnetic field. Their assumption was that once the magnetic field formed, it would block atmospheric particles from escaping into space.

The Rochester team reached a different conclusion.

Simulating the Journey From Earth to the Moon

To better understand how atmospheric particles might reach the moon, the researchers used advanced computer simulations. The team included Shubhonkar Paramanick, a graduate student in the Department of Physics and Astronomy and a Horton Fellow at the LLE; John Tarduno, the William R. Kenan, Jr. Professor in the Department of Earth and Environmental Sciences; and Jonathan Carroll-Nellenback, a computational scientist at the Center for Integrated Research Computing and an assistant professor in the Department of Physics and Astronomy.