Become a fan of Slashdot on Facebook


Forgot your password?
Check out the new SourceForge HTML5 internet speed test! No Flash necessary and runs on all devices. ×
Moon Space Science

New Evidence That the Moon Was Created In a Massive Collision 155

derekmead writes "New evidence that the giant impact hypothesis is correct: A paper published today in Nature shares findings of a chemical analysis of Moon rocks that shows fractional differences between the makeup of the Earth and Moon that most likely were caused by the collision between Earth and a Mars-sized planet around 4.5 billion years ago. Although the two are quite similar, it's been previously shown that Moon rocks lack volatile elements, which suggests they may have evaporated during the incredibly intense heat and pressure created during an impact event. But if the hypothesis that light elements actually evaporated from Moon rocks during their formation is correct, you'd expect to find evidence of elements being layered by mass — heavier elements would condense first, and so on. That process is known as isotopic fractionation — a concept central to carbon dating — and the Washington University team's results suggest they found exactly that (abstract). They compared the blend of zinc isotopes in Moon rocks and Earth samples, and found that the Moon rocks held slightly higher proportions of heavier zinc isotopes. If the Moon was indeed once part of Earth — which has been shown by extensive modeling (PDF) — the difference in the balance of zinc profiles would most likely be explained by lighter zinc isotopes evaporating away following a collision."
This discussion has been archived. No new comments can be posted.

New Evidence That the Moon Was Created In a Massive Collision

Comments Filter:
  • Who DOESNT think the moon was caused by a collision, outside of a few Creationists?

    • The moon was put there by the invisible pink unicorn, her pinkness be praised! Of course, there is no evidence of her having put the moon there because she is invisible.

      • Re:Old news? (Score:5, Informative)

        by Laxori666 ( 748529 ) on Wednesday October 17, 2012 @04:22PM (#41686425) Homepage

        You insensitive clod! The invisible pink unicorn is a demon implanted into the minds of credulous cretins by the Flying Spaghetti Monster to test our faith! Obviously the FSM, his spaghetiness be praised, was the one who created the moon by spontaneously generating a meatball and applying his large-body creation sauce to it. o one listen to parent - he is a deluded fool.

    • Who DOESNT think the moon was caused by a collision, outside of a few Creationists?

      Exactly. We all know it was created by the Divine Light of the Fifth Element as it neutralized the Great Evil.

    • Re:Old news? (Score:5, Interesting)

      by Kittenman ( 971447 ) on Wednesday October 17, 2012 @05:08PM (#41686969)

      Who DOESNT think the moon was caused by a collision, outside of a few Creationists?

      Tut. Look back at the past. I used to be a lot more into astronomy than I am now, and back in the 70s/80s, the thought that the moon was caused by a collision was not laughable, but looked at askance. One thought was that if there was a helluva collision, why wasn't the rest of the planet shattered into fragments (much like the poor chaps in the gap between Mars and Jupiter...). I took the "both formed together, dual planet" thesis as the latest there was 'til I read Bill Bryson (god help me...) in his book "A short history of nearly everything", or some such title.

      Every theory is blindingly obvious and unquestionable, 'til someone proves it isn't. T. H. Huxley read Darwin's "Origin of Species" and thought it stupid of him (Huxley) not to have thought of it. Same here ..

    • It's one of the great strengths of science.... that people can question doctrine, and continue to seek evidence to strengthen or weaken existing beliefs, no matter where in the lifecycle of the belief...

      Provided the research is accurate and sufficiently developed to draw some sort of conclusion, it's good, no matter what the conclusion is, even if it is simply "here is a tiny bit more evidence for an accepted theory"

      Yay science!

    • Until we went to the Moon via Apollo and found the subtle differences in composition of the rocks, when compared to Earth, the leading theory was that it formed simultaneously with Earth as a kind of dual planet.
      • by mcgrew ( 92797 ) *

        Not as a kind of dual planet, although it will be in the future. The orbit of the moon and Earth has its center inside the Earth, making the moon a satellite. It is very slowly moving away from the Earth so at one point the pair's center of orbit will be outside the Earth, at which time it will be a dual planet.

        • by Zenaku ( 821866 )

          Wait is that right? It's true that the barycenter of the earth-moon system is inside the earth, and that the moon is moving farther away.

          But does increasing the distance cause the barycenter to move outside the earth? I would intuitively think the opposite, that as the distance increases it would induce less "wobble" in the earth, moving the barycenter closer to earth's center.

          But I'm no physicist, and I'm not saying you're wrong. Just wondering if someone could explain to me how distance effects the bar

          • by Zenaku ( 821866 )

            Self-replying here, but I just looked up the equations for the 2-body problem, and sure enough, you are right. The math makes it perfectly clear, where intuition falls on its face.

  • by Mister Liberty ( 769145 ) on Wednesday October 17, 2012 @04:12PM (#41686313)

    With some careful interpretation and text analysis of Velikovsky's
    works, we may yet find he predicted this.

    • by jfengel ( 409917 )

      Meaning... if we ignore the predictions that were outright wrong, and infer predictions that weren't actually made from text that could just as easily be used to infer opposite conclusions... then we might alter the consensus that he was a complete loon?

      Whatever works for ya, I guess.

  • I'm guessing this happened before Flash Gordon's time. Who knew that 40's pulp sci-fi was based on facts?
  • by Anonymous Coward on Wednesday October 17, 2012 @04:19PM (#41686391)

    What did the people who only worked 60 hour weeks in grad school believe?

  • I wonder what the size of Earth would be if there was no impact event that created the moon. Anyone?
    • About the size of present earth + present moon, I'd imagine.

      • by emho24 ( 2531820 )
        I guess that is assuming that 100% of the material was absorbed and none escaped. Anyway, just curious.
      • Re:Size of Earth? (Score:5, Informative)

        by SecurityTheatre ( 2427858 ) on Wednesday October 17, 2012 @04:35PM (#41686563)

        Considering it took a Mars-sized object to cause the collision event, and that a pretty substantial amount of mass would have been blasted away at escape velocity, I'm not sure the veracity of your math.

        Of course, you might be roughly right, but probably not for the reasons I think you're implying...

        • I was just trying to be funny, but now that you've made me think about it I'll add a bit to your comment.

          There are two ways to look at it: as if the impact never happened, or as if there was an impact but for whatever reason it didn't break the moon free.

          If there was no impact then we would still be size of earth + size of moon + whatever debris we lost during the impact

          If there was an impact then it would be size of earth + size of moon + size of impactor - debris as Shatrat and Harperska suggested below.


      • by geekoid ( 135745 )

        wouldn't it be earth + moon + object striking the earth at the time?

        • by Shatrat ( 855151 )

          earth + moon + object striking the earth - material ejected at escape velocities from massive explosion

          • by geekoid ( 135745 )

            Since the total gravity would now be stronger then each individual piece, how much would actually permanently escape? Seeing he we don't have any rings, I don't think that much would escape.

        • As mentioned by SecurityTheatre, it would be (earth + moon + impactor) - (sum of material accelerated to escape velocity by impact)

      • - the size of whatever hit us.
    • Just look at the volume of the Moon compared to the volume of the Earth. 22 billion cubic kilometers vs. 1083 billion cubic kilometers (about 2%). If you added that volume back and assumed it distributed evenly, the Earth's mean radius would increase by just under 50km.

      Note: That's assuming there was no extra debris thrown out or outgassed that didn't end up back on the Moon or Earth in the end. Probably not too valid of an assumption.

  • by bennomatic ( 691188 ) on Wednesday October 17, 2012 @04:24PM (#41686447) Homepage
    ...that Pangea (the conglomeration of land which drifted apart to become our current continents) might have been the Earth's "exit wound", where the Moon's material separated. For me, this is a hunch, with no basis in scientific fact, so I'm not going to declare its truth or defend it, but I would not be surprised if, in 10 or 20 years, some evidence were to surface supporting this idea.

    I remember being a kid and thinking that South America and Africa would fit together like a puzzle, and this was long before I'd ever heard of Pangea. Since that time, it's my understanding that irrefutable evidence--basically, the matching of fault lines and mineral components--has been found to support this. Later, I remember having the idea that the Moon may have been spit out of the Earth as the result of a large collision. My hunch was specious as it was based only on the idea that its orbit is perfectly matched with its rotation speed (aka tidally locked), and I understand that it's possible for that to happen in other ways, but this seemed to me the best bet.

    That last idea led to the Pangea idea. Maybe I'll read the freakin' article to see if other people feel the same way.
    • Re: (Score:3, Informative)

      by Anonymous Coward

      Pangaea, Pangæa, or Pangea (play /pænËdÊ'iËÉ(TM)/ pan-JEE-É(TM);[1]) was a supercontinent that existed during the late Paleozoic and early Mesozoic eras, forming about 300 million years ago[2] and beginning to rift around 200 million years ago

      The Moon is thought to have formed nearly 4.5 billion years ago, not long after the Earth.

    • . Later, I remember having the idea that the Moon may have been spit out of the Earth as the result of a large collision.

      Yes, you had the idea after you saw the movie about that idea back in the '60s: []

    • I don't think that that theory would be justifiable, given the proposed hypothesis of a 4.5-billion year old collision. Pangea is nominally 230 million years old, and there was a ton of plate tectonic movement before then.

      That said, I've read the articles referenced, and I don't understand where the introduction gets the idea that this proves the asteroid theory. It looks to me like the same evaporation could occur in the event of a georeactor (which I believe *did* happen, though I also believe that it

      • Do you have a link to any maps that show what you're describing? All the permian-era pangaea maps I'm finding online don't have nearly enough detail to see any of that. Or is it one of those things where you need a graduate degree or a LOT of free time to grok?

        Also, I find myself wishing for the first time that Google Earth had a geologic time slider.

      • 230?

        I think your theory is a tad silly.

        No living thing could withstand an explosion of the size that would eject a moon. I'm sorry, but there has been living things on earth far longer then 230 million years, regardless of what you think about radioisotope dating, nothing can account for this adequately. You mention this being the cause of the Permian extinction, but I find it somewhat hard to believe, since given current ideas about tectonics, etc, there are plenty of small craters that MUST have formed f

        • The permian extinction is unique in that while in other extinction events, you lose up to 70% of the species, in the permian you lost 99% of the species. Whatever happened, it was huge.

          I don't think that just the release of the Siberian traps (on the other side of the globe) would have done it. But that's all we've got... at the moment.

          • The permian extinction killed only 70% of vertebrates, yet 99% of marine species. This, to me, leads researchers toward the conclusion of more varied biosphere changes, rather than a massive single shock like a global shockwave or a massive atmospheric ignition or something...

            I sitll think you grossly underestimate the violence of a moon-creation event. The forces involved would have turned the ENTIRE surface of the earth into liquid rock. It's not something that 2,000 different species of amphibians cou

    • Hello,

      My understanding of current geological theory is that Pangea is just the most recent of a cyclic occurrence of supercontinents.

      There have been multiple time periods in Earth's history when most of the land was in one supercontinent, which then split into continents, only to rejoin again. Wikipedia has the cycle at 300M to 500M years.

      Here's the wikipedia article. []

      So, I think your exit would th

      • Interesting. Of course, the cycle would have had to have started somewhere, and if the whole asteroid-earth-moon thing is true, that could have started a flow that would cause just what you're describing. Basically, if, at the time, the Earth had been a water-covered planet, this sort of collision/ejection could have started a toroid flow which eventually broke up the scar, only to have those features re-coalesce elsewhere on the planet, then break up again, and so on.

        What we could be looking at, effec
        • My gut tells me different. :)

          The supercontinent cycle is driven by the earth's own internal heat, the ringing effect of the impact would probably have damped within days or weeks. I've seen analogies made between the continents on the earth and bits of froth on boiling water: the water pushes the froth around, sometimes it coalesces into one patch, other times it breaks up.

          However, the impact might have contributed a fair bit of the heat that drives the supercontinent cycles, either directly with kinetic

    • My hunch was specious as it was based only on the idea that its orbit is perfectly matched with its rotation speed (aka tidally locked)

      All satellites will eventually become tidally locked to the body they're orbiting. The larger bodies gravity distorts the satellite so that is elongated toway whatever it is orbitting. If the satellite is rotating faster than it's revolving, this bulge has to move along the surface of the satellite, and this flexing gradually drains momentum, slowing it's rotation rate unt

    • Other than Pangaea not forming until 300 million years ago and the moon impact happening 4.5 billion years ago I don't see any problem with your theory.
      • by mikael ( 484 )

        I always thought it was the other way round. The great ring of fire (Pacific ocean area) was where the chunk of Earth which was blown into space and became the Moon.

        Though I found this link (depth of Earth's crust) [], and do wonder whether the Earth could have
        expanded due to nuclear fission.

        Always wondered how the rock and mountains in Afghanistan are over 70 miles deep.

    • Sorry to blow your theory away, but Pangea formed 300 million years ago, the moon was formed somewhere around 4 *billion* years before that.

  • "If the Moon was indeed once part of Earth — which has been shown by extensive modeling (PDF) — the difference in the balance of zinc profiles would most likely be explained by lighter zinc isotopes evaporating away following a collision."

    As a skeptic of the 'giant impact hypothesis' of the Moon's origin:
    Collisions between planetary bodies are too complex to model.
    I won't believe anything based on computer models unless they simulate the interaction of every single particle in the solar system.
    "Garbage in - garbage out."
    They obviously just kept tweaking the model until it gave them the result that they wanted.
    I have an article from a non-scientific magazine in the 1960's that says the Moon drifted gently into orbit around the Earth.

    • There's a difference between moon-creation models and climate change models: The moon creation models are used to explain how something exists today whereas the climate change models are used to predict how something will be in the future. And future predictions tend to have a pretty poor track record.
      • by Pembers ( 250842 )

        Also, if we're wrong about how the moon was formed, the worst that'll happen is that someone has to rewrite a few astronomy textbooks. If we're wrong about humans making the planet hotter (which I don't believe we are), that means rich people don't need to spend a lot of money reducing the amount of greenhouse gases they dump into the atmosphere. Maybe that's why "giant impact deniers" are rather rarer than climate change deniers...

        • by celle ( 906675 )

          " that means rich people don't need to spend a lot of money reducing the amount of greenhouse gases they dump into the atmosphere"

                So it all comes down to a bunch of rich people trying to save some money.

    • In global climate science, while I believe their theories hold some water, there are multiple conflicting models, none of which are possible to compare with existing conditions over a long term (at least not until we have more time to study it).

      The models of the moon, on the other hand, are comparatively simple. The moon is one of the only planetary bodies to have very low levels of heavy metals. This is VERY hard to explain and limits its explanation. Simply modeling the interaction of planetary elements

    • by mikael ( 484 )

      Moon is actually drifting away from Earth - around 5 cm/year. 50 cm/decade, 500cm/century, 50m/millenium, 50km/million years, 50,000km/billion years, 250,000km/5 billion years. But that extends beyond the age of the solar system.

      At the time of the theoretical collision, the Moon was only a third of the distance from Earth than it is today. []

  • A sci-fi author (can't recall who) once wrote in a novel that Earth's crust contains a relatively high percentage of heavier elements because of the Moon. Without Moon's (relatively big, as far as satellites are concerned) gravitational pull, heavier elements would've fallen toward Earth's center leaving only lighter ones to cool down and turn solid on the crust.

    Can somebody more knowledgeable on the field comment on the theory? Is there any truth in this? Is this an important factor on making a planet habi

    • Probably wouldn't have more than a negligible effect -- after all, you don't lighten noticibly when the moon passes overhead.

      The moon can barely manage a tiny slosh when tugging on an entire ocean.

    • by mopomi ( 696055 )

      This is incorrect.

      First, if the moon and Earth were both tidally locked, this might have some ever-so-tiny effect, but probably not enough to notice. There was a time when the fact that the Moon's center of mass is offset from its center of figure was thought to be due to being tidally locked with to the Earthâ"that has been shown not to be the case and the difference is thought to be due to volcanism and large impacts.

      Note that the Earth-Moon's barycenter (center of mass) is located within the interi

  • New Evidence That the Moon Was Created In a Massive Collision

    Better I think would be "New information discovered adds support to theory of moon created by massive collision"

    The headline made it sound like it was already established fact. And even though it's correct use of the word, I think that calling this new discovery "evidence" contributes to this confusion. (though it is the strongest current theory, and will probably eventually be accepted as fact although not likely ever proven)

  • by hemo_jr ( 1122113 ) on Wednesday October 17, 2012 @05:37PM (#41687259)

    There has been a flurry of new models (or significant variations on the old model) suggested recently. They include a smaller than Mars impactor that hit at a higher velocity and a slower impactor that was approximately the same size as the newly formed Earth. Both were inspired by studies that showed that the evection resonance of the Earth-Moon-Sun system would allow for a greater slow down in the rotation of the Earth getting to the contemporary 24 hr day. (see [] et al)

    • I still haven't given up on the scientific theory that "and YHWH set the lesser light in the sky to govern the night".

      That was just before He gave men nipples and women a shriveled weenie and unsealed ball sac.

  • I feel obliged to point out that isotopic fractionation is not "central" to carbon dating. The key to carbon dating is that radioactive carbon-14 decays to nitrogen-14 with a half life of roughly 5700 years, enabling biological material to be dated by its residual carbon-14 content. That is not isotopic fractionation, it's radioactive decay. Isotopic fractionation would be involved if you observed a difference in the ratio of carbon-12 to carbon-13 in plants versus that same ratio in the air.

    • I think he's talking about geological-scale radioisotope dating (of rock strata, for example), and using the term "carbon dating" as a generic.

  • We don't have to exercise ourselves that much to know, actually - just check the headlines at the time. The Guardian puts it most succintly:

    Earth hit by huge asteroid, creates moon

    And from The Sun:

    Rooney injured by space rock

"It's what you learn after you know it all that counts." -- John Wooden