In a few years, NASA will be sending astronauts to the Moon for the first time since the Apollo Era (1969-1972). As part of the Artemis Program, the long-term goal is to create the necessary infrastructure for a “sustained program of lunar exploration.” The opportunities this will present for lunar research are profound and will likely result in new discoveries about the formation and evolution of the Moon.
In particular, scientists are hoping to investigate the long-standing mystery of whether or not the Moon had a magnetosphere. In anticipation of what scientists might find, an international team of geophysicists led by the University of Rochester examined samples of lunar material brought back by the Apollo astronauts. Based on the composition of these samples, the team determined that the Moon’s dynamo was short-lived.
The research was led by John A. Tarduno, the William R. Kenan Jr., Professor, of Geophysics and the dean of research for Arts, Sciences & Engineering at the University of Rochester. He was joined by researchers from Rochester’s Department of Earth and Environmental Sciences, the Planetary Science Institute (PSI), Michigan Technological University (MTU), the Geological Survey of Japan, and universities across the US, UK, Canada, and France.
The lunar glass samples tested by Rochester scientists were gathered during NASA’s 1972 Apollo 16 mission. (University of Rochester photo / J. Adam Fenster
For the sake of their study, the team examined samples of lunar glass from a young impact crater (about 2 million years old). This impact caused material on the surface to comingle with the material in the mantle that dates back to shortly after the Moon formed (ca. 4.5 billion years ago). In the past, examination of lunar rocks has revealed indications of strong Earth-like magnetization, indicating exposure to a magnetic field.
In the case of Earth, our planetary magnetic field (aka. magnetosphere) is the result of a geodynamo deep in our planet’s core. This is created by the movement of the molten outer core around the solid inner core, which generates the powerful electric currents that make up the Earth’s magnetic field. For some time, scientists have understood the important role our magnetic field plays in the maintenance of habitability here on Earth.
Were it not for this field, the surface of our planet would be bombarded by intense amounts of solar radiation and cosmic rays. In addition, interaction with charged particles from the Sun (solar wind) would have slowly stripped our atmosphere away over the course of eons (which is what happened on Mars). While the Moon has no magnetic field to speak of today, it did at one time, which raises the question of how long it existed.
Moreover, scientists have many unresolved questions about how the Moon could have sustained a magnetic field given its size and mass. As Tarduno explained in a recent Rochester Newscenter release:
“This is a new paradigm for the lunar magnetic field. Since the Apollo missions, there has been this idea that the moon had a magnetic field that was as strong or even stronger than Earth’s magnetic field at around 3.7 billion years ago.
The core of the moon is really small and it would be hard to actually drive that kind of magnetic field. Plus, the previous measurements that record a high magnetic field were not conducted using heating experiments. They used other techniques that may not accurately record the magnetic field.”
A subsample of lunar glass is placed in
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