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Listen to part of a lecture in an astronomy class
Okay
The collection of moon rocks
That astronauts brought back to earth in the early ninenine hundred sevenseventies provided ded with a lot of information about the nature of the moon
But there's one thing about the rocks
That's especially puzzled scientists ever since these missions
Why did so many of them have a magnetic signature evidence of having been magnetized in the past
After all we know the moon unlike earth has no magnetic field
Today well let's back up a bit
Here and discuss earth's magnetic field
It's explained by the dynameo theory
The dynamo theory explains how earth generates a long lived global magnetic fields
Now we know earth has a molden metalalic core
That is a core made up largely of hot liquid iron
Well as the warmer molecules of this iron liquid rise the cooer porporand sink in a circulatory emotion
This circulating mettalicclick would inside earth along
With the rotation of the earth creates electric currents
And these electric currents in turn create earth's magnetic field
A moltain core that generates magnetic field is a dynamo
And the action of this dynamo magnetizes rocks on earth
But the moon doesn't have a magnetic field now and scientists of long believe that it has never had one why well for one thing
The moon is cold
And it was also thought that the moon was too small to have had a molden core
So it came as a big surprise
When astronauts returned with rock samples
That had been magnetized ed ever since ce those early emissions
Scientists have been debating the answer to this question
Some scientists have argued that the shock of the impact of media rights and asteroids left a magnetic signature around the moon rocks
See three point nine billion years ago
Rouadtvely soon after the moon formed
It underwent a period of heavy media rights
Asterroid id bombardment
The scientists thought it was the impact during this period of bombardment
That a shocked door altered many of the moon rocks and left a magnetic signature on them
Other scientists however have theerorized that at one time soon after the moon formed
It could in fact have had a molden core and a magnetic field like girth does
And that it was this not medior strikes
That was the source of the magnetic signatures on the moon rocks
So who's right well
The very detailed recent analysis of a particular moonrock known as the tructoe may finally ally ped ed shed some light on this debate the tructoe is made of tructilight
A combination of minerals
They crystalized very early in the moon history
And i mean very early this rock is about four point three billion years old
And the magnetic signature found on tracto was very different
Than the signature on other moon rocks
It suggests that the rocks had a very long period in a magnetic environment millions of years
You say magnetization from a media right generates a short lived magnetic field
Which results in a certain magnetic signature and the tructoto just doesn't show that in laboratory tests
Sciensts found it had been exposed to two stable and intense magnetic events
Each followed by a long cooling period
The first event of the one were most interested in occurred about four point two billion years ago
About three hundred million years after the moon
Formed of the time
When the moon would most likely have had a liquid metalic core
And because of the prolonged nature of the magnetic event
Scientists speculate that it was caused by a magnetic field
Generated by a multon metalic core and not a media strike
So even if tructoo had been subjected to that later bombardment that occurred three point nine billion years ago
It's not the source of the magnetization that scientists found
Well
This lunar dynamo theory certainly is very appealing to many of us for one thing
We've been trying to explain the origin of the moon for a long time
And this theory fits very nicely with the most widely accepted hypotheis of the moon's origin that giant impact hypothesis
The giant impact hypothesis also allows for the possibility
That the moon had a small motcore ore
I'll talk about that theory and other ways to two theories dib in in a few minutes
Now admittedly having only one luter rocke's evidence isn't enough for a lot of scientists
But it's a good start
