New research shows that Earth's magnetic field has helped deliver atmospheric particles to the lunar surface over billions of years.
The moon's surface may be more than just a dusty, barren landscape. Over billions of years, tiny particles from Earth's atmosphere have landed in the lunar soil, creating a possible source of life-sustaining substances for future astronauts. But scientists have only recently begun to understand how these particles make the long journey from the earth to the moon and how long the process has been taking place.
New research from the University of Rochester, published in Nature Communications Earth and Environment, shows that Earth's magnetic field may actually help guide atmospheric particles-carried by solar wind-into space, instead of blocking them. Because Earth's magnetic field has existed for billions of years, this process could have steadily moved particles from Earth to the moon over very long periods of 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).
The findings suggest lunar soil may not only hold a long-term record of Earth's atmosphere but could be even more valuable than scientists once thought for future space explorers living and working on the moon.
Clues from lunar soil
Soil brought back to Earth by the Apollo missions in the 1970s has provided scientists important clues. Studies of these samples show that the moon's dusty surface-called the regolith-contains volatile substances such as water, carbon dioxide, helium, argon, and nitrogen. Some of these volatiles come from the sun's constant stream of charged particles, known as the solar wind. But the amounts-especially of nitrogen-are too high to be explained by solar wind alone.
In 2005, a team led by researchers from the University of Tokyo proposed that a portion of the volatiles may have come from Earth's atmosphere. They argued this could only happen during a time before Earth developed a magnetic field, since they assumed the magnetic field would prevent atmospheric particles from escaping into space.
But the URochester researchers found the process may work differently.
Simulating how Earth's atmosphere reached the moon
The URochester team-including 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-used advanced computer simulations to model how and when the regolith might have acquired the elements found in the Apollo samples.
The researchers tested two scenarios. One modeled an "early Earth" without a magnetic field and under a stronger solar wind. The other modeled a "modern Earth" with its strong magnetic field and a weaker solar wind. The simulations showed that the particle transfer works best in the modern Earth scenario. In this case, charged particles from Earth's atmosphere are knocked loose by the solar wind and guided along Earth's magnetic field lines. Some of the field lines stretch far enough into space to reach the moon. Over billions of years, this funneling effect has helped tiny amounts of Earth's atmosphere settle on the lunar surface.
Preserving the past and supporting the future
The long-term exchange of particles means the moon may hold a chemical record of Earth's atmosphere. Studying lunar soil could therefore give scientists a rare window into how Earth's climate, oceans, and even life evolved over billions of years.
The long-term, steady transfer of particles also suggests the lunar soil contains more volatiles than previously thought. Elements such as water and nitrogen could support a sustained human presence on the moon, reducing the need to transport supplies from Earth and making lunar exploration more feasible.
"Our study may also have broader implications for understanding early atmospheric escape on planets like Mars, which lacks a global magnetic field today but had one similar to Earth in the past, along with a likely thicker atmosphere," Paramanick says. "By examining planetary evolution alongside atmospheric escape across different epochs, we can gain insight into how these processes shape planetary habitability."
This work was funded in part by NASA and the National Science Foundation.
