Our Magnetic Satellite, The Moon

The Magnetic Moon

Magnetic analyses of the Moon’s crust and Apollo samples show that our Moon generated magnetic field billions of years ago. The first lunar magnetic field was possibly even more potent than the Earth’s magnetic field is today. 

Nevertheless, it has been unclear when the lunar magnetic field stopped. A team led by scientists from the famous MIT has used NASA’s Apollo 15 samples to pin down the timing of the Moon’s dynamo’s end.

It shows that it discontinued sometime between around 1.92 and 0.80 billion years ago. 

There Is a Core Crystallization Inside The Moon

These new findings are consistent with the predicted continuance of core crystallization on the Moon. 

This suggested mechanism for powering the lunar dynamo could have produced a weak and long-lived magnetic lunar field in the latter part of our Moon’s history. 

The MIT-led investigation group intends to measure the Moon’s first magnetic field’s direction in hopes of gathering more information about our Moon’s evolution.

The Magnetic Moon. Credit: Canva.

Why Does Our Moon Not Have a Magnetic Field Today?

The answer is that because the liquid outer lunar core is mainly made of electrically conductive iron, the fluid motions generate electric currents, producing a global magnetic field. 

But our Moon, nevertheless, is too small, so it doesn’t have sufficient energy in its core to support a magnetic field.

Tina Dwyer is fascinated with the Moon. The former Caltech undergrad has been interested in science and astronomy ever since she was a child. 

Close up Moon. Credit: Canva.

Charting The Magnetic Fields of Small Lunar Rocks, Glass Particles In The Moon’s Soil.

However, it wasn’t until she took a (SURF) or a Summer Undergraduate Research Fellowship project at Caltech that her enthusiasm for the Moon and planetary science lighted. 

Her Summer Undergraduate Research Fellowship project propelled her interest in the Moon into high gear. 

Tina worked with a professor of geobiology Joe Kirschvink and then-postdoc Ben Weiss on charting the magnetic fields of small lunar rocks—glass particles found in the Moon soil. Tina spent two summers on that project and thought it was awesome.

Later, in the spring of 2005, Tina got a planetary interiors class taught by a professor of planetary science, Dave Stevenson. 

And for the class, students had to do a short study project, and one of the proposed topics was on answering a decades-long lunar mystery.

The Moon at dusk. Credit: Canva.

The Moon Is Too Small To Maintain A Magnetic Field

How did the old moon power its now-defunct magnetic field? Tina grabbed onto that idea.

Earth’s magnetic field is powered by force from its core, which makes the molten outer lunar core churn. And because the molten outer core is essentially made out of electrically conductive iron, the fluid motions generate electric currents, creating a global magnetic field. 

The Moon, nevertheless, is too small, so it doesn’t have sufficient energy in its core to provide and maintain a magnetic field. 

So, experts were then confused when the NASA Apollo astronauts returned magnetic lunar rocks, which could solely occur in an ambient magnetic field. 

And since then, scientists have been attempting to come up with a satisfying explanation.

The Moon in the dark. Credit: Canva.

The Physical Stirring Could Have Made the MMoon’s Magnetic Field Of Its Molten Core. 

And for forty years, people have been sitting there, scratching their heads, going, how will we solve this? For her investigation project, Dwyer suggested that instead of being powered by heat, like in the Earth, our Moon’s magnetic field could have been made by the physical stirring of its molten core. 

And after finishing Caltech in 2006, Tina went to graduate school at the famous University of Washington, where she read experimental geochemistry. 

Now Tina is pursuing her Ph.D. at the well-known UC Santa Cruz, where she’s turned to planetary science and the research project she began at Caltech. 

So, with Francis Nimmo and Stevenson of UCSC, Tina refined her earlier work, and the team has now published their findings in the famous journal Nature.

And their story pairs in with the previous thoughts of how the Moon evolved and formed in its orbit. 

Moon, credit: Canva.

The Earth’s Gravity Attracts The Moon

The Earth’s gravity attracts the Moon in a way that makes the Moon’s molten mantle and core spin around axes at a slight angle about each other. 

And as a consequence, instead of spinning as a single object, the mantle and core rotate separately. 

The differences in their movements are pretty slight today. Still, the Moon, which is currently shifting away from Earth at a pace of a few centimeters per year, was much closer to our Earth during the Moon’s magnetic field existed several billion years ago. 

And because of its closer range, the gravitational interactions were stronger, leading to a more significant variation in rotation between the mantle and core. 

The Moon. Credit: Canva.

The Moon Drifts Farther Away From Earth

Tina and her co-workers calculated that, in the past, the variation was pronounced enough to create a magnetic field.

Furthermore, as the Moon drifted farther away over time, the variation in motion lessened, and the magnetic field eventually died. 

So, the fact that we have a way to turn off the magnetic field is a fascinating aspect of this model, Tina says. However, she emphasizes that further research, including improving computer models to investigate the mechanism in detail, is essential to show that the theory is viable.

That’s it; thanks for reading. I hope you enjoyed this short article. If you want to know more secrets about our Moon, head over to this article: 11 Things You Didn’t Know About the Moon.

Watch this video about Moon’s magnetic field. Credit: Newsy.
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