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Mystery of Moon's Magnetic Field Deepens

internal dynamo cosmic impacts precession asteroids

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#1 Hum

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Posted 19 May 2013 - 14:35

The moon generated a surprisingly intense magnetic field until at least 3.56 billion years ago, 160 million years longer than previously thought, a new study reports.

These findings could shed light not just on the magnetic field of the moon, which is now extremely weak, but on that of asteroids and other distant worlds, investigators added.

Earth's magnetic field is created by its internal dynamo, which itself is generated by the planet's churning molten metal core. Research increasingly suggests that the moon once had a dynamo as well, with evidence of magnetism found in lunar rocks returned by Apollo astronauts.

Models of the moon's core suggest its dynamo should have lasted only until about 4.1 billion years ago. However, last year, scientists revealed that the moon possessed a magnetic field for much longer than previously thought, with a powerful dynamo in its core from 4.2 billion years ago to at least 3.72 billion years ago.

Researchers have proposed two possibilities to explain why the moon's dynamo lasted so long. One possible explanation is that giant cosmic impacts set the moon lurching enough to drive its dynamo. Another explanation has to do with how the moon's core spins around a slightly different axis than its surrounding mantle layer, generating wobbles — known as precession — that could dramatically stir its core.

The cosmic-impact idea is supported by the fact that the moon experienced massive collisions until around 3.7 billion years ago, such as the one that created the 715-mile-wide (1,150 kilometers) Mare Imbrium, among other craters.

However, the dynamo generated by each impact would have lasted for a mere 10,000 years or so, scientists say. In contrast, if precession drove a lunar dynamo, the moon could have continuously possessed a magnetic field until as late as 1.8 billion years ago.

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#2 Torolol

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Posted 19 May 2013 - 14:40

is there any theory to revitalize the moon's magnetosphere?

and of course if possible to revitalize mars's magnetic too ...

#3 OP Hum

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Posted 19 May 2013 - 15:24

^ I'm sure there is a way. ;)

#4 DocM

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Posted 19 May 2013 - 15:42

is there any theory to revitalize the moon's magnetosphere?

and of course if possible to revitalize mars's magnetic too ...


Magnetospheres are generated by the liquid part of the (mostly iron) core spinning, and yhe moon's doesn't because it cooled and solidified. To start it back up you'd need to re-melt it - no small task. Don't hold your breath.

Earth's core is still molten because it's 1) much larger, so it cools slower, and 2) there are trace radioactive isotopes (potassium, uranium etc.) whose decay heats it, further slowing its cooling.

#5 Osiris

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Posted 19 May 2013 - 15:47

I've had enough of the moon and its games, now that Jack Bauer is coming back I say we finally make this moon reveal its secrets!

#6 Growled

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Posted 20 May 2013 - 03:16

If it had a strong magnetic field, what effects did it have on early Earth?

#7 DocM

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Posted 20 May 2013 - 04:18

Not much so far as life was concerned - it was largely gone by then and pretty far away to begin with. Might have had varying effects on the solar wind; additionsl shielding at some times, opening Earth up to a bit more exposure at others.

#8 ShareShiz

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Posted 20 May 2013 - 04:22

If it had a strong magnetic field, what effects did it have on early Earth?


Really crazy tides :|

#9 Raa

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Posted 20 May 2013 - 04:26


Just dig down and take a look? :p

#10 OP Hum

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Posted 20 May 2013 - 15:58

If it had a strong magnetic field, what effects did it have on early Earth?


The Moon has not always been orbiting Earth -- it was later 'adopted'. ;)

#11 DocM

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Posted 20 May 2013 - 17:08

The Moon is OF Earth - a large impactor splashed debris into orbit and it coalesced into the Moon. Some of that debris was iron etc., and more was crust & mantle.

#12 Xenomorph

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Posted 20 May 2013 - 17:13

Where in the Bible does it mention all this?

#13 Zlain

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Posted 20 May 2013 - 17:16

Where in the Bible does it mention all this?


If I could dislike this post, I would.


Quite interesting information. If the magnetic field was restarted, would it actually give us more shielding or less, because that is bound to influence the magnetic field of the Earth, but its the alignments of those fields which are important (which is why satellites are more prone to SPE damage at the polar horns than low inclined orbits).