Moon's Metal-Rich Craters Challenge Popular Theories About Its Origin (upi.com) 68
schwit1 shares a report from UPI: The most popular theory of the moon's origins contends the satellite was formed when a Mars-sized object collided with Earth, vaporizing large portions of Earth's upper crust. While Earth's upper crust is poor in metals, new research -- published Wednesday in the journal Earth and Planetary Science Letters -- suggests the moon's subsurface is surprisingly metal-rich, undermining the satellite's proposed origin story. Authors of the new study suggest planetary scientists consider alternative theories for the moon's formation.
It's possible the collision that forged the moon was more violent than scientists thought, gouging out even deeper portions of Earth's crust and mantle. It's also possible the moon experienced an unusual cool-down process, post-collision -- a process that left the moon with large concentrations of metal.
It's possible the collision that forged the moon was more violent than scientists thought, gouging out even deeper portions of Earth's crust and mantle. It's also possible the moon experienced an unusual cool-down process, post-collision -- a process that left the moon with large concentrations of metal.
Asteroids? (Score:4, Interesting)
I thought asteroids were metal rich. If the earth/moon split was caused by an asteroid then we have a source of metals
Re:Asteroids? (Score:5, Informative)
The more likely reason won't be discovered until there's a way to image the interior of the moon.
But there's two possible scenarios:
a) the moon is the earth's core, or split from the earth's core when the planet was still in a hot state, hence it's round shape. This could have been caused by something zooming through it.
b) the moon is the core of another planet (take note of all the asteroids between mars and earth) that was captured.
Like scenario A is entirely believable, just look at how a Newton's cradle works. Something of X mass entered the core of the planet and sent something of equal mess out of it.
Scenario B also has evidence , but like I said in the first line, without being able to see the interior to see if it's the same make up of earth, we wouldn't be able to tell. The fact that it has moonquakes tells us it's still seismically active, or presumably. (It could also just be gravity pull.)
But both scenarios require information that we can't get at this time, and it could still be possible that both are wrong as well. We may need to actually visit other moons to see if that's how other moons formed.
Like it's far more likely that the moons of most other planets in the system are formed in a similar way, where they simply formed by gasses collecting and forming mass, and sucking more mass towards them as they developed their own gravity, and eventually reached an equilibrium where they neither add or lose gas mass so that the remaining solids stay put as they cool down. Earth loses twice as much mass as it gains, but that likely wasn't always the case, and a Mars scenario where the magnetic field is lost forever is likely the end game for life on Earth. Meanwhile the moon should have a magnetic field if it's core is the same as earth.
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I'm not so sure A is possible. I feel as though something large enough and moving fast enough to displace the core of a molten planet will have enough inertia to escape. I'm neither a mathematician, nor a physicist, but I would imagine the momentum window for such an object would be exceedingly small, if it even exists at all.
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Plus the moon is round because of gravity pulling it into that shape, not because of its starting temperature.
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Not necessarily - think a head-on collision between billiard balls - the impactor comes to a complete stop while 100% of momentum is transferred to the target.
Of course the Earth and its hot core were not rigid objects, so it still seems sort of unlikely.
I rather like the synestia hypothesis - the impact was severe enough to vaporize both the impactor and original Earth into a rapidly spinning cloud which then re-condensed into the current moon and planet. https://www.ted.com/talks/sara... [ted.com]
I wonder if suc
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No. Period. It's not only possible that both of those wild ass guesses are wrong, but so probable that you can damn near say it's a certainty that they are.
A) The moon formed well after the Hadean period started to cool, when there was plenty of crust formed. Not to mention due to physics this scenario is retarded the second you actually think about it. Something hitting a mass that large, at that energy would blow the mass apart and fling the resulting gasses too far apart to reform.
B) also retarded, unle
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Correct me if I'm wrong, but the moon may have the same makeup as the Earth's core and still not have any significant magnetic field *if* the core has cooled to ambient (or close to ambient) temp.
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But if you took the composition of the Earth's core, and cooled it to the temperature of the Moon's surface and interior, then yes, you'd have no net magnetic field because you'd have no fluid conductor to create a turbulence-powered dynamo. You're right about that. The fluid need not be metallic - several of the outer planet's icy satellite
Re:Asteroids? (Score:5, Informative)
Meanwhile the moon should have a magnetic field if it's core is the same as earth.
Considering that Earth's field is caused by our core spinning at 1000s of MPH generating electricity, and we believe that the moon's is not, so no. It is believed that the core IS similar to earth's, but, like you said, we really need a lot more evidence and measurements up there.
Hopefully when we put a base up there, more nations will start doing research on the moon itself.
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We don't need to put bases up there to get that data. We're running a seismograph on Mars ; we can put another one on the Moon pretty much next week, if there were anything significant to gain by it. Well, a couple of years to spec
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the moon is the earth's core, or split from the earth's core when the planet was still in a hot state, hence it's round shape
The round shape doesn't really indicate anything - any body of sufficient size and mass (which the moon is well above) will eventually pull itself into a roughly spherical shape just due to gravity.
As to your insistence that it's a planetary core (either ours or another), that doesn't make a lot of sense. The density of the moon is 3.34 g per cubic cm. Earth's density is 5.51 g per cubic cm. If Earth lost it's core to become the moon it would be less dense, not more.
With the density situation being what
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We can tell from the density of the moon whether it has a lot of metal in its core. We know the total mass of the moon, and thanks to Apollo and probes know what the surface is made out of.:
Top layer + bottom layer (center) = total mass
Shortened: T + B = M
We know T and M and thus can infer B. B is not unexpectedly large, meaning the moon is probably not a left-over core (mostly rocky, not metals). This also means the real puzzle is
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Also, the Moon is billions of years old and is absolutely covered in impact craters from meteorite strikes and it doesn't have a water cycle or subduction zones, etc. Wouldn't we expect the upper layer of the moons surface to be covered in meteorite material, which is generally pretty metal-rich? Material that might have heavily infiltrated the crust of the moon? Beyond that, we expect the denser stuff to sink in a molten body, but how would the much lower gravity of the moon be expected to affect that proc
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> Material that might have heavily infiltrated the crust of the moon?
How? Without a water cycle or subduction zones, etc. the metal would stay right where it landed, as a concentrated metallic deposit somewhere near the bottom of the crater.
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I'm assuming that it stayed more or less right where it landed, but that where it landed went from being the surface to the subsurface over time. Partly because the moon would have been molten at the surface originally, then would have gone through hundreds of millions of years of volcanic activity. So all that material at the surface would have mixed with lava flows. After that, meteoric bombardment would have deposited more and more material on top both as actual meteoric ore and ejecta and presumably the
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If the surface were still liquid, the asteroid metals would still have plenty of time to settle into the core (and there would be no impact crater). Drop a lump of iron into a pool of molten rock and it will fall to the bottom just as it would in water, and for the same reason - metals are among the densest elements. It would fall a little slower than in water, and leave a trail of molten metal behind it as it melted while it fell, but that liquid would also rapidly settle. About the only way it *wouldn't
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If the surface were still liquid, the asteroid metals would still have plenty of time to settle into the core (and there would be no impact crater).
The absence of an ancient crater would be expected. I'm talking about very old impacts where the metallic contents of the meteorites would have become part of the crust, no crater would be expected to be left behind. The study we're discussing is talking about more recent impacts revealing more metal in crust material than is expected. As far as the surface being liquid and the material settling to the core, there's no particular reason to expect that a cooling celestial body will have a surface that solidi
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> there's no particular reason to expect that a cooling celestial body will have a surface that solidifies evenly from the outside in
Not perfectly evenly, no. But certainly it cools from the outside in, because the outside is the only part that can shed heat. And so long as it remains liquid, convective currents will tend to keep things reasonably evenly heated at a given depth. Of course both radioactive decay and pressure-heating both generate more heat the deeper you go.
Stalagmites, etc. are rather
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It certainly cools from the outside in, but there's a pressure gradient and mass separation that can lead to alternating layers of liquid and solid. That exact situation exists on Earth, so there doesn't seem to be any reason that it couldn't exist elsewhere. That combined with volcanism can lead to a frequently liquid surface that can absorb meteorites and eventually turn into metal-rich crust.
Stalagmites are a special case, but were simply presented as an example that unequivocally doesn't require pressur
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Oh, you mean the asthenosphere? The "liquid layer" on which the granitic continental crust floats, with a congealed skin of basalts and gabbros flooring the oceans.
Well, yes, that is the model that is in the textbooks. But when you get into actually reading the papers on igneous petrogenesis and the sonic properties of rocks (as measured by mapping the attenuation of earthquake waves in various directions) ... you realise
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The contrast with sedimentation on the Earth is that on the Moon there is generally no liquid phase in which "cementation" of one grain to another can happen. So the mineralogy and diagenesis [wikipedia.org]of sediment from impact debris remains essentially that of the
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There's your error. The prevalence of metallic asteroids is closer to 1% than it is to 5%. Don't let Star Trek and Star Wars and such like confuse you - the asteroid belt in the solar system has a lot more ice and rock than it does metal.
Another useful couple of data to keep in mind when you're thinking of such things - the Moon is about 1% of the mass of the Earth, and the asteroid belt is about 1% of the mass of the Moon. Which doesn't make for dramatic scenery to app
Moon took ur metal ... but seriously, (Score:1)
if this is true and our moon came to exist in a different way than we thus far assumed, how did it and what would that mean for our understanding on planet forming? Also, our Moon might well be the stepping stone we need for solar system exploration. What is keeping us?
Re:Moon took ur metal ... but seriously, (Score:5, Funny)
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Pretty obvious when you think about it (Score:2)
"What is keeping us?" (Score:2)
What is keeping us is simply the will to prioritize space over other matters.
The US DOD budget is 686 billion dollars. NASA's is only 22 billion. A single aircraft carrier being built in the current program costs 1/2 of NASA's entire budget.
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And yet we're still allocating more money to our space program than any other entity (by a long shot):
https://www.statista.com/stati... [statista.com]
What is keeping us? (Score:2)
Money
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What is keeping us?
2019 Pentagon budget, without the Black Budget or intel agencies - $750 billion
All NASA budgets since its foundation, including Apollo, combined - $650 billion
Average Pentagon spending - 45% of Federal budget
Peak NASA spending in 1969 - 4.5% of Federal budget
Current NASA spending - 0.45% of Federal budget
This is why we can't have nice things.
"Every gun that is made, every warship launched, every rocket fired signifies, in the final sense, a theft from those who hunger and are not fed, those who are cold and
The Werewolves Made It (Score:4, Funny)
So they would have something to bark at.
It's a prank (Score:2)
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It is the glory of God to conceal a matter, But the glory of kings is to search out a matter.
--Proverbs 25:2
"O, Almighty God, I am thinking Thy thoughts after Thee!"
--Kepler
I'd characterize it more as "giving humans a goal to their existence" than "trolling", but, it wouldn't be the first time.
Moon only has a small metal core (Score:4, Interesting)
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Unlike other large rocky bodies in the solar system, the Moon only has a small metal core. The findings in this paper are revealing metal on or just under the surface. If that metal had been there when the Moon formed, and was still mostly molten, it would have sank into the interior. Something must have added it as a layer after the Moon differentiated early in its formation.
I'm just a layman, but if the excess metal is being found at or near the surface in craters then it seems the obvious source for those metals would be whatever made those craters.
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One theory is a dead-planet's core shattered in a nearby collision, perhaps involving proto-Mars or proto-Venus, and rained down metallic asteroids.
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FTFY
The smallest planet is Mercury (unless you count the ice ball Pluto, which is not likely to have any significant metal core), with a core about 1800km in radius (the core of Mars is a similar size).
If you collected all the asteroids into a lump, it'd be about 1200km in diameter (being rather generous).
So ... if you took a dead planet, removed the core and disposed of the silicate 3/4 of the volume (for a terrestrial-like planet) to "somewhere else", then s
alt.chrome.the.moon (Score:2)
Calcium (Score:3)
Which metal? Please tell me the moon is rich in calcium.
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Which metal? Please tell me the moon is rich in calcium.
As a matter of fact it is, compared to Earth:
Lunar meteorites also have high concentrations of calcium (CaO) compared to most terrestrial rocks (except, of course, those rocks rich in calcite, like the limestones that plot around 50% CaO). [wustl.edu]
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Happy?
Do you want to see it? Look at the Moon. See the relatively dark grey ovals making up the "Man's" eye sockets and the splodge of "his" right cheek. Those dark grey bits are relatively poor in calcium. The area which is relatively light grey, and particularly where "his" left cheek and jowl are - that's an area called the "Southern Highlands". It is largely a rock type called anorthosite, and it is relatively rich in calcium. In the mineralogical norm of analysi
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There has been very little tectonic movement in the Moon since its formation, and essentially none since the surface solidified. The flooding of the maria basins brought mantle material to the surface, but this was caused by impactors puncturing the crust rather than by tectonic action.
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Ah. That makes sense, unfortunately since we have no crust left from that time period it's hard to be sure what the initial composition ever was.
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Lest it sound like I'm playing the "turtles all the way down" card, but with giant impacts ..
Saw a 2 year old science show that discussed this- (Score:2)
Theory at that time was multiple smaller impacts would preferentially orbit deeper higher-metal-content material from the earth.
Can we rule out a metal rich earth? (Score:2)
Just speculating, but what if earth's crust used to be more metal rich? After the initial formation, there could be more metals in the crust.
Then, the energy released by the moon's initial impact would have disrupted enough of the crust to cause more of the metals in earth's crust to sink to the core - perhaps through faster plate tectonics, the heat generated by the impact, etc.
While the moon, being a smaller body, cools faster and is less tectonically active at the time, and thus retains more metals
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The "putative Moon-forming impact" (far and away the leading hypothesis for forming the Moon) would have completely disrupted the Earth's crust, and most of the mantle to something like a thousand kilometre's depth. Models of the impact have the Earth squished to about
Metal rich craters? (Score:3)
Aren't most meteorites composed of high densities of metals? And aren't most craters on the moon from meteors/meteorites? And why the hell does somebody as stupid as me put these two things together when the science bros are trying to tie it to the Earth's composition?
I feel like this is much ado about nothing. Unless there's some sort of funding drive involved I haven't sorted out yet. Then it makes perfect sense.
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No, actually metal-rich asteroids are fairly rare and so considered extremely valuable for the future of space colonization.
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Aren't most meteorites composed of high densities of metals? And aren't most craters on the moon from meteors/meteorites? And why the hell does somebody as stupid as me put these two things together when the science bros are trying to tie it to the Earth's composition?
Recognizing your own stupidity is a step forward. It is possible you may be able to recognize in yourself a textbook case of Dunning-Kruger Syndrome -- having no idea how useless your notion is since you know nothing of the subject.
You have not even looked at the TFA. Do you know what metals they are even talking about? It is iron and titanium only, and titanium is NOT notably abundant in meteors.
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Boy, do some people have Hollywood-fed images of planetary science.
Billions of years of metallic asteroid impacts? (Score:1)
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There aren't enough metal-rich asteroids to account for the quantity of metals they found.
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At 200-odd km, could I be somewhere else if it somehow touches the Earth. I promise I'll take video. Not that there will be many people to send it to.
I wonder how SkypeZoomFacebookvideo and the like would work with a 10 minute time-of-flight for TCP/IP packets?
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Leeloo did it (Score:1)
Have these scientists not seen the Fifth Element. That is obviously how the moon was created!