typodupeerror

## Molten Core Inside The Moon?47

Posted by timothy
from the love-and-warm-mushy-stuff dept.
beggs writes: "The Times (free reg et al.) is running an article about the possibility of a molten core inside the moon and that this, if confirmed may lend support the the theory that the moon is the child of a violent collision between mother earth and some other heavenly body in the distance past."
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## Molten Core Inside The Moon?

• #### Even if it does have a molten core (Score:3, Informative)

<ObviousGuy@hotmail.com> on Monday May 13, 2002 @11:19PM (#3514803) Homepage Journal
The plate tectonics that would have ensued from having an active core (like Earth's) has ceased, for quite a long time too.
• #### Aren't there easier tests? (Score:2, Insightful)

Measuring fluctuations in the Moon's size obviously tell you if it is solid or not but what about looking at the magnetic field. If the core of the Moon is liqued, then you wouldn't you see a large magnetic field from the free flowing ions in the core? That is what is responsible for the Earth's field.
• #### Re:Aren't there easier tests? (Score:2)

The Moon appears to once have had a magnetic field, but if our theories of field generation are right, it's rotating too slowly now to have any real field.
• #### Re:Aren't there easier tests? (Score:1)

It rotates at a rate of about once a month. That's why the same side is always facing us. The word "rotate" here is a little misleading. The moon acts just like a ball attached to a string acts when it is swung around. The side that the string is attached to is always facing the center, or your hand which is rotating the string. So technically the moon is rotating because it faces the opposite direction every ~30 days but it's not just a coincidence that the rotation of the moon is exactly equal in time to it's revolution around the earth. Like a ball on a string.
• #### Re:Aren't there easier tests? (Score:2)

Yes, exactly. This rotation is thought to be too slow to support a strong field, particularly in a body with such a small, if any, core.
• #### Re:Aren't there easier tests? (Score:1)

I think the poster meant the rotation of the core within the crust (which would produce a field) - not that of the moon around the earth.
• #### Silly scientists.. (Score:1, Funny)

by Anonymous Coward
It was proved (through observation) many years ago that the moon is made of cheese. The reason the government keeps the moon "rocks" is because they're so delicious. Moon cheeseburgers are the best food in the solar system... and don't forget the yummy bacon and moon cheesefries.
• #### Re:Silly scientists.. (Score:3, Funny)

It was proved (through observation) many years ago that the moon is made of cheese.

Now we know that it also has a rich-'n-creamy center! Mmmmmm... I'm hopping it's nougat, topped with caramel.

• #### Re:Silly scientists.. (Score:2)

Unfortunately, it's one of those stinky French cheeses.

Good with fondue.
• #### Energy (Score:2, Interesting)

IF we had a moon colony how would a molten core compare to solar cells as an energy source?

Might be worth looking at.

• #### Re:Energy (Score:2)

A molten core would allow for continuous Geothermal energy (methinks) which would be more useful than solar, since any given location on the moon is only facing the sun for half of each month.

BTW... love the sig.
• #### Re:Energy (Score:2)

...continuous Geothermal energy...

Yeah, this would be the Holy Grail of power sources for a moon colony. There would be a lot of energy down there, much more than we could use.

The only problem I could see is the same one which stops us from using geothermal effectively here; we can't drill deep enough to get a large enough temperature differential to make it worthwhile. Perhaps some engineer could elaborate on this...

• #### Re:Energy (Score:3, Insightful)

IF we had a moon colony how would a molten core compare to solar cells as an energy source?

Solar would be better.

Especially with no atmosphere or weather to degrade the incoming sunlight, solar cells work quite well.

Geothermal is a pain to work with under the best of circumstances (you can only build a large-scale plant (no small power sources)), and even if the moon has an energy-producing core (tidally kneaded or (like Earth's) radioisotope-powered), the amount of energy flowing out of it is small compared to Earth's (no volcanism or rapidly convecting mantle). This means that the yield from geothermal on the moon will under the best of conditions be much lower than on Earth.

Given that solar power is so convenient, I don't see any strong reason to use geothermal. Power storage for half a month isn't *that* hard, and if you need enough power to make storage impractical, you can put big mylar mirrors in orbit around the moon to reflect enough sunlight to supply your photocells (probably cheaper than a power cable around the equator).
• #### Re:Energy (Score:2)

If you want to use geothermal energy, you need active geologic activity at the surface. The Moon doesn't have that, based on the many, many observations we've made of the surface. If there is a molten core at all, it's a tiny fraction of the volume, deep in the interior.
• #### life on our own moon (Score:1)

With a warm core, there is possibility (although slim) for life to survive in air tight pockets beneath the surface and toward the warmth of the core. This would be a great discover for mankind, however slim the odds.
• #### Re:life on our own moon (Score:1)

Mm. Don't hold your breath. There may be a possibility that life could survive in airtight pockets toward an interior warm core, but I don't see how there's any possibility that it could evolve there. ...or that we could find it without dismantling the moon.
• #### Geothermal maybe? (Score:2)

Could this possibly lead to a cheap method of power generation on the moon in the future?
• #### The way he says it... (Score:1)

you would think the following logic was being applied: Earth has molten core. Moon has molten core. Thus, since they both have a molten core, the moon must have come from the earth!

• #### Re:Its not The Times (Score:1)

Hear, hear. This is more evidence of the unthinking U.S.-centric assumptions of much (most?) of what gets posted here.
• #### No way (Score:3, Insightful)

on Tuesday May 14, 2002 @05:09AM (#3516003)
Having a molten core would NOT lend support to the theory that the moon splintered off of the Earth. In fact, the non-existence of a molten-core would better lend support to that theory than a molten core. This is simply because if the moon splintered off of the earth, it is going to be one giant rock. How does one get a molten core from just a rock? Does anyone else see what I'm saying?
• #### Re:No way (Score:1)

No way yourself. It wouldn't be a giant rock. It'd be the product of gravity acting on a cloud of dust ejected in space after the collision, much like Earth and the Sun were formed. Did you really think we thought a large object hit Earth, and ejected a perfectly spherical rock?
• #### Re:No way (Score:2, Informative)

What a lot of people are missing is the fact that the moon is in such an orbit that only one side faces us at any given time (look for yourself.... heh). This orbit is far to delicate for any captured rock, or huge chunk of earth that was smashed off by an asteroid could create, it had to have been that the moon was an actual part of the earth, but gave the earth a lop-sided form. So centripital (spelling?) force caused that chunk to rip off from the earth, creating the moon we have today.

(no, it doesn't have to be necessarily a chunk, but most likely a big scoop pf molten rock... from when the earth was in a molten state.)

Did you really think we thought a large object hit Earth, and ejected a perfectly spherical rock?

Well thats how everything started. Basically huge chunks of rock slammed together to make the planets, and over time, smaller ones filled in the gaps, the pressure created a molten core, and the core smoothed everything out.
• #### Re:No way (Score:3, Interesting)

Darwin's (no, George Darwin, Charles's son) idea about planetary fission to form the Moon doesn't work. There's insufficent angular momentum in the system to make it work. The giant impact model is the ONLY model that makes sense right now. (The tidal locking of the Moon causing it to show us one face at all times has nothing to do with anything.)

In fact, the original poster is correct: if the Moon formed in a giant impact, it appears that it should be almost all rock akin to Earth's mantle. The iron and other metallic elements would have sunk into the interior of the Earth, being lost to the disk of debris what would go on to form the Moon.
• #### Re:No way (Score:2, Interesting)

most likely a big scoop pf molten rock... from when the earth was in a molten state

The earth IS in a molten state as we speak! There's a little crust on the outside, but, proportionally speaking, it's many many times thinner than the shell of an egg. The earth could be hit by a large celestial object TODAY, (even a 200-mile wide blob of frozen ammonium, which is VERY cold) and tomorrow you wouldn't be able to tell that the earth had EVER had a crust. It's not that the force of the impact would melt the entire crust, it's just that it would break the shell and let all the hot insides come out and melt the crust.

• #### Re:No way (Score:3, Informative)

What a lot of people are missing is the fact that the moon is in such an orbit that only one side faces us at any given time

Yes, this is true... it also has nothing to do with how the moon formed. Angular momentum transfer from tidal forces automatically forces an orbiting body into just such a configuration. It's called being tidally locked. This same process has caused the earth's rotation to slow, and to increase the average radius of the moon's orbit.

Doug
• #### Re:No way (Score:1)

How does one get a molten core from just a rock?

The molten core of the earch IS rock - molten rock! i.e. that stuff you see coming out of a volcano is very hot, and hence liquid, ROCK. That comprises the major part of the earth's mass.

• #### non sequitir (Score:1)

What in the world does "molten core" have to do with "split off from Earth"?! The thermal time constant of the Earth is only a few million years -- the core isn't molten because the Earth is still cooling, it's molten because of the decay of radioactive nuclei, primarily uranium. The moon's thermal time constant would be even shorter, so if the core is still molten, it would have nothing to do with a violent creation.
• #### The Most Important Question (Score:1)

How many licks does it take to get to the molten core?

(Let's just hope that some owl doesn't come and take two licks and bite right to the core, forever leaving the problem unanswered)

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