A new study by the Massachusetts Institute of Technology (MIT) has revealed that the Moon used to have a magnetic field of its own billions of years ago. The lunar magnetic field was twice as strong as that of the Earth’s and was the strongest about 4 billion years ago when the Moon was closer to the Earth.
Just like the Earth’s magnetic field protects its ozone layer from being ripped apart by the solar winds, the lunar field was also capable of shielding it from the Sun.
However, over the years, as the Moon began moving away from the Earth, its core began to harden. The further it drifted, the weaker its magnetic core got, finally phasing away altogether one day, the study found.
According to Benjamin Weiss, professor of Earth, Atmospheric, and Planetary Sciences at MIT, the lunar dynamo died around 1-1.5 billion years ago, after the Moon’s core crystallised completely.
Before this, the Earth’s gravitational pull created a buoyant movement of the electrically charged liquid in the Moon’s core that in turn produced the dynamo. Naturally, therefore, once the liquid hardened, it stopped producing the dynamos required to keep the magnetic field working.
“We’ve shown that the dynamo that produced the moo’s magnetic field died somewhere between 1.5 and 1 billion years ago and seems to have been powered in an Earth-like way.”
Weiss and his team studied lunar rocks brought back by US space agency NASA’s Apollo Mission. In many of those rocks, which date back millions of years, they found signs of a strong magnetic field of about 100 microteslas. As against this, Earth’s magnetic field at the moment is 50 microteslas, which means, half of what Moon’s used to be.
In another lunar rock sample studied by the group of researchers, a much less potent magnetic field of 10 microteslas was found. At first, they thought this must be because two mechanisms were at play for the dynamo. The first one though more powerful, was short-lived, while the second one sustained itself for another 2.5 billion years.
Elaborating the importance of this research and how it would change our understanding of the cosmos, the lead author of the study said: “There are several ideas for what mechanisms powered the lunar dynamo, and the question is, how do you figure out which one did it? It turns out all these power sources have different lifetimes. So, if you could figure out when the dynamo turned off, then you could distinguish between the mechanisms that have been proposed for the lunar dynamo. That was the purpose of this new paper.”
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