For billions of years since the formation of Earth and the Moon, solar radiation and our planet’s magnetic field have been driving a complex and invisible process. Parts of Earth’s atmosphere are transported to our moon and remain in its soil.

Earth’s atmosphere and magnetic field.
Source: phys.org

Transfer of Earth particles to the Moon

The surface of the Moon may not be just a barren, inhospitable place. Over billions of years, tiny particles from Earth’s atmosphere have settled on the lunar soil, creating a potential source of substances necessary for the survival of future astronauts. But it is only recently that scientists have begun to understand how these particles make their long journey from Earth to the Moon and how long this process takes.

New research from the University of Rochester, published in the journal Communications Earth & Environment, shows that Earth’s magnetic field may actually help guide atmospheric particles carried by the solar wind into space, rather than blocking them. Since Earth’s magnetic field has existed for billions of years, this process could have gradually moved particles from Earth to the Moon over a long period of time.

“By combining data on particles preserved in lunar soil with computer simulations of the interaction of solar wind with Earth’s atmosphere, we can trace the history of Earth’s atmosphere and its magnetic field,” says Eric Blackman, professor of physics and astronomy at the University of Rochester.

Research findings indicate that lunar soil may not only contain long-term data about Earth’s atmosphere, but may also be even more valuable than scientists had thought for future space explorers who will live and work on the Moon.

Hints on the lunar soil

Soil brought back to Earth by the Apollo missions in the 1970s provided scientists with important clues. Studies of these samples show that the dusty surface of the Moon, called regolith, contains volatile substances such as water, carbon dioxide, helium, argon, and nitrogen. Some of these volatiles came from the constant stream of charged particles from the Sun, known as the solar wind. But their abundance, especially nitrogen, is too great to be explained by the solar wind alone.

In 2005, a group of scientists led by researchers from the University of Tokyo hypothesized that some of the volatile substances could have come from Earth’s atmosphere. They argued that this could only have happened at a time when the Earth did not yet have a magnetic field, since, in their opinion, the magnetic field would have prevented atmospheric particles from escaping into space.

But researchers at the University of Rochester have discovered that this process may work differently.

Role of the magnetic field in particle transport to the Moon

The URochester team includes Shubhonkar Paramanick, a graduate student in the Department of Physics and Astronomy and a Horton Fellow at LLE; John Tarduno, the William R. Kenan, Jr. Professor of Earth and Environmental Sciences; and Jonathan Carroll-Nellenback, a computational scientist at the Center for Integrated Research and Computational Technologies and an associate professor in the Department of Physics and Astronomy, used advanced computer simulations to model how and when regolith could have acquired the elements found in the Apollo samples.

The researchers tested two scenarios. One modeled the “early Earth” without a magnetic field and under the influence of a stronger solar wind. The other modeled the “modern Earth” with its strong magnetic field and weaker solar wind. The simulation showed that particle transport works best in the modern Earth scenario.

In this case, charged particles from Earth’s atmosphere are knocked out by solar wind and directed along Earth’s magnetic field lines. Some of these lines extend so far into space that they reach the Moon. Over billions of years, this funnel effect has caused small amounts of Earth’s atmosphere to settle on the Moon.

Preserving the past and supporting the future

The long-term exchange of particles means that the Moon can store chemical data about Earth’s atmosphere. Therefore, studying lunar soil can give scientists a rare opportunity to learn how the climate, oceans, and even life on Earth have evolved over billions of years.

The long-term, continuous transport of particles also indicates that lunar soil contains more volatile substances than previously thought. Elements such as water and nitrogen could enable humans to stay on the Moon for longer periods, reducing the need to transport supplies from Earth and making lunar exploration more feasible.