The Moon absorbed Earth’s atmosphere over billions of years

Since the early 1970s, when NASA’s Apollo missions brought samples from the Moon to Earth, scientists have wondered about traces of volatile substances such as water, CO2, helium, argon, nitrogen, present in regolith – the surface layer of soil on the Moon.

They then realized that some substances, including nitrogen ions, originated in Earth’s upper atmosphere and were most likely blown to the Moon by solar winds. For the past 20 years, the most popular hypothesis has been that the matter transfer occurred only before the Earth formed a magnetic field because this invisible force could keep atmospheric ions from being blown away.

However, in new research published in the journal Communications Earth & Environmentthe authors combined data from Apollo samples with computer models simulating the evolution of the Earth’s magnetosphere and found that this hypothesis was not correct. Instead, atmospheric ion migration is strongest whenever the Moon passes through the Earth’s magnetic tail – the largest part of the magnetosphere that always points away from the Sun.

Models show that, instead of preventing atmospheric ions from being blown away, magnetic field lines in the Earth’s tail act as “invisible highways”, guiding them towards the Moon to be incorporated into the topsoil. Thus, the process of atmospheric ion transfer may have begun shortly after the magnetosphere formed about 3.7 billion years ago and continues to this day. This result shows that the lunar soil can store “long-term data storage” about the Earth’s atmosphere, and also opens up the possibility that the Moon contains valuable resources for astronauts living and working on this celestial body in the future.

“Our study could help better understand atmospheric loss on planets like Mars, which once had magnetic fields similar to Earth’s,” said University of Rochester planetary scientist Shubhonkar Paramanick, lead author of the new study. Future research could help better understand how these processes shape the ability to support life on planets, he added.

In addition, lunar soil collected on upcoming missions, such as NASA’s Artemis or China’s Chang’e, could allow scientists to fill in gaps in Earth’s geological history.