Moon had its own magnetic field that died a billion years ago: Study

Moon lost its magnetic field billions of years ago which was probably even stronger than the Earth’s field at present, a study said. Researchers, in the new analysis, tried to pin down the timing of the end of the lunar dynamo, which was active during the period 4.25 to 3.56 billion years ago.

The intensity of the present-day magnetic field across much of the lunar surface indicates that the moon currently does not have a global magnetic field. But the Apollo samples from the moon were analysed and its paleomagnetic measurements established that it generated a core dynamo with surface field intensities measuring to several tens of microtesla.

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Core crystallisation phenomenon

A team of researchers from the Massachusetts Institute of Technology (MIT), with the help of the National Aeronautics and Space Administration (NASA), found out that the lunar dynamo ended around one billion years ago. According to the study, an important mechanism of core crystallisation favoured the lunar dynamo. The liquid core’s electrically charged fluid was buoyantly stirred due to the crystallisation of the moon’s inner core and produced the dynamo.

“The magnetic field is this nebulous thing that pervades space, like an invisible force field,” said Benjamin Weiss, professor of earth, atmospheric, and planetary sciences at MIT.

The co-author further added, “We’ve shown that the dynamo that produced the moon’s magnetic field died somewhere between 1.5 and 1 billion years ago, and seems to have been powered in an Earth-like way.”

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Earlier, scientists had discovered signs of a strong magnetic field in lunar rocks as old as 4 billion years and measuring around 100 microtesla, which is almost twice the present-day Earth’s magnetic field. Later, Weiss’s team studied the sample collected from the Appollo mission and found a much weaker magnetic field.

“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,” said Weiss.

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