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Moon Space Science

Findings Cast Doubt On Moon Origins 233

Posted by samzenpus
from the moon-mystery dept.
sciencehabit writes "A new analysis of isotopes found in lunar minerals challenges the prevailing view of how Earth's nearest neighbor formed. Geochemists looked at titanium isotopes in 24 separate samples of lunar rock and soil, and found that the moon's proportion was effectively the same as Earth's and different from elsewhere in the solar system. This contradicts the so-called Giant Impact Hypothesis, which posits that Earth collided with a hypothetical, Mars-sized planet called Theia early in its existence, and the resulting smash-up produced a disc of magma orbiting our planet that later coalesced to form the moon."
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Findings Cast Doubt On Moon Origins

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  • by Anonymous Coward on Monday March 26, 2012 @01:09PM (#39475967)

    That's no moon!

  • by fluffythedestroyer (2586259) on Monday March 26, 2012 @01:11PM (#39475983) Homepage
    We have the technology to find and look very deep or far where isotopes are or where the fartest solar system is. But yet, I can't find my damn keys in my house sometimes.
  • by Anonymous Coward

    So, if it wasn't a big impact, what was it? What's the next best theory?

    • by Anonymous Coward on Monday March 26, 2012 @01:15PM (#39476037)
      Anthropogenic global warming.
    • by jdgeorge (18767) on Monday March 26, 2012 @01:44PM (#39476425)

      So, if it wasn't a big impact, what was it? What's the next best theory?

      Well, according to TFA:
      "One possibility is that a glancing blow from a passing body left Earth spinning so rapidly that it threw some of itself off into space like a shot put, forming the disk that coalesced into the moon. This would explain why the moon seems to be made entirely of Earth material. But there are problems with this model, too, such as the difficulty of explaining where all the extra angular momentum went after the moon formed, and the researchers aren't claiming to have refuted the giant impact hypothesis."

      • by Jmc23 (2353706)
        So basically the prevailing theory before the big impact theory?
      • by adamchou (993073)
        wouldn't a glancing blow theory require that the object that glanced the earth to be immense in size? it couldn't have just been a meteor or asteroid. i'd imagine it'd be a planet sized object. which leads me to wonder, what is a planet doing just floating around like that?
    • by VernonNemitz (581327) on Monday March 26, 2012 @02:02PM (#39476673) Journal
      The giant impact scenario can still make sense. All we need to do is assume both the Earth and the other object formed in the same zone (distance from sun). That's the most critical thing, since we can expect any one zone, all around the sun, to be fairly consistent in its isotopic composition. So, each gathered up lots of debris while forming, and their collision constituted one of the last events that made the Earth a planet (per modern definition: a planet has to clear its zone of all large debris).
      • by Michael Woodhams (112247) on Monday March 26, 2012 @06:41PM (#39479409) Journal

        I was thinking this. However, now you require two planetary bodies to occupy the same orbital zone for long enough for them to form without colliding, and yet to collide later on. This is tricky, but perhaps not impossible. They might initially form in some orbital resonance (probably one of the Trojan points) and then some other body comes by and destabilizes the orbits. (I don't know if Trojan points are stable in a still-accreting-planets disk.)

        Another possibility is there were two collisions: Theia itself was formed from proto-Earth in a collision, and then later caused the moon-formation event.

    • by JustOK (667959) on Monday March 26, 2012 @02:31PM (#39476963) Journal

      We should demand to see its birth certificate.

  • "We are not brothers, hanger-on..."

    ['ruff for cartoon]

  • Not a contradiction (Score:5, Interesting)

    by Anonymous Coward on Monday March 26, 2012 @01:18PM (#39476087)

    It doesn't contradict it at all. The current version of the impactor theory pre-supposes that Theia was formed at Earth's L4 or L5 point. There, the fractional distillation effect in the solar nebula would give the same Ti isotope ratios as in Earth, since Theia would be orbiting at the same distance. Formation at L4 or L5 also gives a nicely low impact energy, agreeing with what is needed to form the moon.

    • by Quaoar (614366) on Monday March 26, 2012 @01:28PM (#39476225)
      This doesn't work. The fractional element abundances depend not only on the location in the protoplantery disk, but on the timescales of accretion, which depend on the mass of the object accreting. Thus, even if you formed Theia in L4/L5, the isotopic ratios should be different, as the two objects will have different masses.
      • by icebike (68054) * on Monday March 26, 2012 @02:18PM (#39476829)

        The location of Theia's formation at 4 or L5 would be close enough to earth that the accretion would of the same material. Further if Theia were at L4 it would lead earth in the orbital path, 60 degrees ahead, and would tend to preferentially sweep the protoplanetary disk, before earth's mass rendered any advantage. Any differences in ratios would be small at the time of impact.

        Bear in mind that anything at the the Lagrange points must necessarily be insignificantly small relative to the earth. As soon as it stops being so, the likelihood of it staying at the Lagrange point becomes nil. I remain unconvinced that a planet could form at L4 or L5 and become large enough such that any impact would eject a mass as large as the moon. Drift should occur long before it acquired enough mass. (Earths orbit is not circular, rather it is elliptical, and as such the Lagrange points are really unstable Lagrange "areas").

        Disregarding my doubts, when a body formed at L4 or L5 does drift, and impact earth, that impact would scatter its content over the surface of the earth such that we would, after all these billions of years, be hard pressed to distinguish it from earth's original composition. Similarly, the moon would be composed of the same material sources, a combination of both Theia and Earth materials.

        Any subtle differences in accretion would be completely masked by impact mixing.

        However, the same could be said about any body impacting the earth. The likelihood of such a body remaining intact (bottling up any difference in isotopic ratios) is virtually nil, and both earth and moon are going to be covered with the same relative ratios in any method which postulates the moon being formed from ejecta from an earth impact.

        At best this finding puts to rest the long discredited "captured moon" theory.

        • by Quaoar (614366) on Monday March 26, 2012 @02:29PM (#39476947)
          The problem is that the ratio of Earth's mantle to Theia's mantle matters in the combination, even if mixing is efficient. The Earth's mantle is fully convective, and around 6 times the mass of the impactor's mantle, which means that you have to really fine-tune the conditions to achieve the exact right mixture. A good analogy would be trying to mix milk and water in a glass such that the fluid that splashes out of the glass has the same fraction of milk to water as the fluid remaining in the glass. With the original Oxygen isotope constraint, 95%+ of the lunar mantle needed to originate from the Earth, which is in direct conflict with the giant impact simulations that have been performed (which find 80% coming from the *impactor*), even for iron-rich impactors that preferentially remove Earth's mantle. This new constraint, if I am reading the paper correctly, is even stronger than the Oxygen isotope constraint, being at the part per million level rather than the part per ten thousand level.
          • by icebike (68054) * on Monday March 26, 2012 @02:55PM (#39477231)

            The Earth's mantle is fully convective, and around 6 times the mass of the impactor's mantle,

            Wait, what? Where did you get 6 times? And where did the impactor get a mantle? That number is sheer conjecture, and the existence of a mantle makes so sense until you have an impactor large enough to have a differentiated body. That hasn't been proven.

            Moon's core is different from earth's [wikipedia.org] by our best guesses. But the surface accretion in the eons after any impact is going to accumulate the same combination of protoplanetary disk material and ejecta material.

            We've barely scratches the surface of earth, let alone the moon. These isotope measurements are akin to determining the structure of a large building by examining a paint chip scraped off of each.

            And using hind sight, doesn't ANY outcome appear to be the result of "fine tuning"? Isn't any such argument just another form of intelligent creation dogma?

            • by Quaoar (614366) on Monday March 26, 2012 @04:09PM (#39478135)
              The preferred giant impact model has a Mars-sized impactor with a core-to-mantle ratio equal to the Earth's, with approximately 30% of its mass being in an iron core (http://adsabs.harvard.edu/abs/2004Icar..168..433C). Mars is ~1/6th the Earth's mass. In this impact, the material liberated that eventually forms the moon is iron poor, as the iron core of the impactor sinks into the Earth. That has been the interpretation as to why the Moon's iron core is so small (no more than 3% its total mass), so in this sense the giant impact model produces a satisfactory outcome. Some fraction of the lunar surface is accumulated over the 4 billion years since the Moon formed, but this layer is thought to be very thin, and the meteorites + Apollo samples we use to measure the moon's isotopic ratios come from a range of depths that probe significantly deeper than this surface layer. The fine-tuning argument comes from the fact that for an arbitrary combination of impactor + Earth mass, impact angle, velocity, etc, you'd expect a scatter in the isotope ratios consistent with the typical scatter measured between other bodies in the solar system (say that between Mars and the Earth). Fine-tuning is often employed in intelligent design arguments as they rely on the anthropic principle, but as there's no reason to require the Earth and Moon to have identical isotopic compositions to explain the existence of life, there is no particular reason to favor any particular outcome over the myriad of other outcomes for this particular measurement.
  • Huh? (Score:3, Insightful)

    by Lumpy (12016) on Monday March 26, 2012 @01:19PM (#39476099) Homepage

    "Geochemists looked at titanium isotopes in 24 separate samples of lunar rock and soil, and found that the moon's proportion was effectively the same as Earth's and different from elsewhere in the solar system"

    and

    " This contradicts the so-called Giant Impact Hypothesis, which posits that Earth collided with a hypothetical, Mars-sized planet called Theia early in its existence, and the resulting smash-up produced a disc of magma orbiting our planet that later coalesced to form the moon."

    SO discovering that the Moon's and Earths isotopes match means it could NOT have formed from a splash of magma from the earth?

    This whole thing contradicts it's self. How do they know that the other body was not a twin of the earth and formed from the same disc of dust and debris? do they have samples of this other planet?

    • by canajin56 (660655) on Monday March 26, 2012 @01:24PM (#39476161)
      You could RTFA instead of calling bullshit based on your understanding of the summary, but that would be work. The problem is that it's highly unlikely that in such a scenario, any less than 40% of the moon would be made up of magma from Theia.
    • by mhajicek (1582795)
      They're asserting that 40% of the Moon's mass must have come from the impactor, and thus would have a different isotope balance.
      • Re:Huh? (Score:4, Insightful)

        by demonbug (309515) on Monday March 26, 2012 @01:43PM (#39476403) Journal

        They're asserting that 40% of the Moon's mass must have come from the impactor, and thus would have a different isotope balance.

        That's clear, but why would the impactor necessarily have a significantly different isotopic ratio than the Earth? Yes it theoretically had a significantly different mass, but the distance from the sun was similar. How much understanding do we have of the variation in these isotopes on other planetary bodies? We have samples from what, the Earth, the Moon, and probably asteroids (very small mass so not too surprising if their isotope ratio is very different)? Possibly Mars? That doesn't seem like a whole lot of data to base models of isotope variation on, so it seems like a weak argument to say that Theia should have had a substantially different isotopic ratio for oxygen and titanium than the Earth. It would be nice if this was discussed in the article, but it isn't (and the link to the original journal article is broken so I can't check for myself).

      • by Soralin (2437154)

        Wouldn't a significant percentage of the mass of the surface of the Earth also have come from the impactor, and therefore also have had it's isotope balance altered in the same way?

      • by mcmonkey (96054)

        They're asserting that 40% of the Moon's mass must have come from the impactor, and thus would have a different isotope balance.

        Unless the same percentage of the Earth's mass came from the impactor as that of the moon.

      • by icebike (68054) *

        Their assertion is highly suspect at best.

    • SO discovering that the Moon's and Earths isotopes match means it could NOT have formed from a splash of magma from the earth?

      No, it means that it probably could not have formed from a splash of magma that came mostly from Theia, which would be the case under the Giant Impact Hypothesis.

      • by lgw (121541)

        But isn't the surface of the moon different in composition on the nearside and the "dark" side (certainly different in appearance)? And aren't all the samples from the near side?

        As long as the splash of magma form the Earth was denser than that from Theia, that's the part we'd land on and collect samples, no?

    • by jamstar7 (694492)
      IANAAP, but wouldn't some of the isotopes of the impacting rock show up in the Moon's assay, which would give the geochemists the opinion of the Impact Theory being the correct one?
  • by vlm (69642) on Monday March 26, 2012 @01:19PM (#39476105)

    Conclusion sounds good, written logic is horrible.

    found that the moon's proportion was effectively the same as Earth's

    This contradicts the so-called Giant Impact Hypothesis, which posits that Earth collided with a hypothetical, Mars-sized planet called Theia early in its existence, and the resulting smash-up produced a disc of magma orbiting our planet that later coalesced to form the moon.

    Does not explain why that doesn't work. The summary makes it sound very likely that something "smooshed off" the earth and became the moon, because both have the same ratios. Also does a poor job of explaining the more likely alternative explanation, by not discussing it at all. Fail.

    I think part of the fail is assuming:

    different from elsewhere in the solar system

    That means we've sampled everything in the entire solar system both now and infinitely in the past? ha ha I think not.

    • They've sampled a big number of meteorites, from several parts of the Solar System. Also, they don't need to sample them over time because they know how isotopes change, and thus only need a snapshot.

      The conclusion seems quite well fundamented.

    • by Tablizer (95088)

      This is perhaps the key to your question: "Computer models indicate that, for the collision to remain consistent with the laws of physics, at least 40% of the magma would have had to come from Theia."

      To fit the current Theia model, the isotopes of the moon should be noticeably different from Earth because moon's material would be about 40% from Theia. The chance of Theia having identical isotopes to Earth is considered an unlikely coincidence. Moon should be "polluted" with non-Earth isotopes, giving differ

  • Occam's Razor (Score:3, Interesting)

    by Iniamyen (2440798) on Monday March 26, 2012 @01:20PM (#39476113)
    Is there evidence to suggest that the simplest explanation (accretion disk formed the earth and the moon at roughly the same time, along with all the other rocky planets) is not the correct one? I honestly can't remember, it would be nice for someone more knowledgeable than I to set me straight. We seem to be obsessed with "fantastic" explanations, maybe because we are trying to get folks interested in science. The simple explanation is still pretty friggin' interesting to me.
    • by phrostie (121428)

      Agreed but it's not as likely to get grant money or published

    • Re:Occam's Razor (Score:5, Informative)

      by ShanghaiBill (739463) on Monday March 26, 2012 @01:51PM (#39476543)

      Is there evidence to suggest that the simplest explanation (accretion disk formed the earth and the moon at roughly the same time, along with all the other rocky planets) is not the correct one?

      Computer simulations have shown that the accretion disk theory is unlikely. The moon is HUGE. Compared to the size of the mother planet, it is by far the biggest in the solar system. It is also really far from the earth, nearly 400,000km. By comparison, the distance from Mars to Phobos is less than 10,000km. Most of the mass in an accretion disk should have fallen to earth, with a small amount forming a few very small moons, orbiting closely.

    • by Xtifr (1323)

      As I understand it, the mass, composition, and age of the moon are all wrong for that that theory (which was the prevailing hypothesis when I was young).

      Wikipedia says [wikipedia.org]: "the co-formation of the Earth and the Moon together in the primordial accretion disk [...] does not explain the depletion of metallic iron in the Moon." It also doesn't explain the 40 million years or so difference in age betwen the Earth and the Moon.

      • by samkass (174571)

        As I understand it, the mass, composition, and age of the moon are all wrong for that that theory (which was the prevailing hypothesis when I was young).

        I remember having a poster when I was young (in the 70's) that showed how the moon formed by a lopsided Earth wobbling off a big glop of moon and having it slowly cool and spiral outward.

        • by Cytotoxic (245301)

          I had the same (or similar) poster from National Geographic. It showed the three possible origins of the moon on one side and a highly detailed map of the moon on the other. Nice map.

          FWIW- the three possible origins of the moon were: Budding from angular momentum, co-formation in the same location and capture of a rogue planetessimal from elsewhere in the solar system. If I recall correctly, budding and capture were considered long-shot ideas. Interesting that the currently prevailing theory was not o

    • If they both formed from the same accreation disk, the composition of the Earth and the Moon would be different, not similar.

  • I don't see how this contradicts anything. If a mars sized body impacted the earth, I doubt there was much that wasn't rendered into magma and mixed together.

  • That's what I read on the Internet.
  • by Kojow777 (929199) on Monday March 26, 2012 @01:34PM (#39476287)

    It's times like this that I'm happy to be a creationist.

    • Same here. We have it so easy, man. Whenever things don't make sense, God did that (in all His mysterious ways). None of that pesky data collection and analysis here, science LOSERS!

      Man I love knowing that all answers to all questions boil down to the same two answers, which are: "but the times you saw one set of footprints in the sand were the times I carried you!" and "because Jeebus died for you, THAT'S why, you dirty, dirty microscope sinner!".

      We still on for Wednesday's "New Research? Still Go
  • Headline vs. Article (Score:5, Informative)

    by Sean_Inconsequential (1883900) on Monday March 26, 2012 @01:37PM (#39476331)

    From the article: "[...]and the researchers aren't claiming to have refuted the giant impact hypothesis."

  • by Spy Handler (822350) on Monday March 26, 2012 @01:38PM (#39476349) Homepage Journal

    You know how you can tell astronomy is a real science? The people doing it are willing to look at new evidence... even if it casts doubt on their current beliefs.

    • They do not insist that the "science is all settled".
    • They do not belittle those who come up with hypothesis or evidence that contradicts their current views. (notice that they didn't call this new researcher a "Denier")
    • They do not take polls amongst themselves and form a concensus, and then insist they're right on the strength of the fact that they have formed a concensus.

    If you see people in a field of "science" doing any of the above, it's not science but something else entirely.

    • by Xtifr (1323)

      Anyone who's old enough to remember the first moon landing knows that. Our notions of how the solar system was formed, and in particular, how the moon was formed, have undergone drastic modification as physical evidence started coming in. When I was young, the accreted-from-the-same-cloud theory was still the prevailing one. My parents may well remember the Mars-has-canals theory.

    • In all scientific fields, some theories are more supported by facts than others, thus they are more likely than others.

      This is also the case for astronomy.
      Here is an example where those who choose to ignore mountains of facts in order to deny the most supported theories are called deniers by astronomers:

      http://blogs.discovermagazine.com/badastronomy/2009/06/09/im-skeptical-of-denialism/ [discovermagazine.com]

      • by lgw (121541)

        No, that's nothing to do with astronomy. That's just a statement of religious beliefs that happens to be made by an astronomer, speaking outside of his field.

        Yes, yes, I know. I'm a heretic to your religion, and that makes me a sinner and just a big meanie. Guilty.

        • by free2 (851653)

          Are calling a religion the previous sentence "some theories are more supported by facts than others" ?

          This is strange because all religions think that their beliefs don't need to be supported by facts.

          • by lgw (121541)

            You might be surprised how many believers in a religion think the facts support their religion. A quite bright math prof once told me "you can't get away from the fact that a man came back from the dead."

            Real science: when the measurements don't fit the theory, adjust the theory.

            Not science: we'll just keep adjusting the measurements, always in the direction that tends to confirm our theory.

            Real science: "Some of my conclusions are based on modeling. All the details of my model can be found in Appendix B.

            • Do you think that "some theories are more supported by facts than other theories" ?

              If yes then you have to accept the right of climate scientists to say that "some climate theories are more supported by facts than other climate theories".

              The IPCC reports acknowledge that other theories could be right in the end, that is why they use the word "likely" for their predictions instead of saying "we are certain that...".

              So calling the IPCC reports "religious" is clearly a mistake. No religion uses the word "likel

  • by Ultra64 (318705) on Monday March 26, 2012 @02:37PM (#39477015)

    It amazes me that so many allegedly "educated" people have fallen so quickly and so hard for a fraudulent fabrication of such laughable proportions. The very idea that a gigantic ball of rock happens to orbit our planet, showing itself in neat, four-week cycles -- with the same side facing us all the time -- is ludicrous. Furthermore, it is an insult to common sense and a damnable affront to intellectual honesty and integrity. That people actually believe it is evidence that the liberals have wrested the last vestiges of control of our public school system from decent, God-fearing Americans (as if any further evidence was needed! Daddy's Roommate? God Almighty!)

    Documentaries such as Enemy of the State have accurately portrayed the elaborate, byzantine network of surveillance satellites that the liberals have sent into space to spy on law-abiding Americans. Equipped with technology developed by Handgun Control, Inc., these satellites have the ability to detect firearms from hundreds of kilometers up. That's right, neighbors .. the next time you're out in the backyard exercising your Second Amendment rights, the liberals will see it! These satellites are sensitive enough to tell the difference between a Colt .45 and a .38 Special! And when they detect you with a firearm, their computers cross-reference the address to figure out your name, and then an enormous database housed at Berkeley is updated with information about you.

    Of course, this all works fine during the day, but what about at night? Even the liberals can't control the rotation of the Earth to prevent nightfall from setting in (only Joshua was able to ask for that particular favor!) That's where the "moon" comes in. Powered by nuclear reactors, the "moon" is nothing more than an enormous balloon, emitting trillions of candlepower of gun-revealing light. Piloted by key members of the liberal community, the "moon" is strategically moved across the country, pointing out those who dare to make use of their God-given rights at night!

    Yes, I know this probably sounds paranoid and preposterous, but consider this. Despite what the revisionist historians tell you, there is no mention of the "moon" anywhere in literature or historical documents -- anywhere -- before 1950. That is when it was initially launched. When President Josef Kennedy, at the State of the Union address, proclaimed "We choose to go to the moon", he may as well have said "We choose to go to the weather balloon." The subsequent faking of a "moon" landing on national TV was the first step in a long history of the erosion of our constitutional rights by leftists in this country. No longer can we hide from our government when the sun goes down.

    • I like your theory and would like to subscribe to your news letter. One thing bothers me though, where is George Soros in all of this? Did... oh god, did he fund this entire project?

  • by Diamonddavej (851495) on Monday March 26, 2012 @03:57PM (#39477995)

    Recent re-analysis of lunar volcanic samples shows the interior of the Moon is allot wetter then we thought. Some parts of the Moon interior, at least, contain as much water as the Earth's upper mantle, far wetter than predicted by the Giant Impact Hypothesis (the water should have boiled off).

    Less sophisticated analysis in the 1970s indicated the Moon is very dry (less than 50 parts per million water). But water was lost to the vacuum of space during lunar volcanic eruptions, giving a false impression the Moon was dry. New techniques detected water trapped inside fluid inclusions (bubbles) in olivine crystals, showing the interior of the moon is quite wet. Zhang at al. 2012 is one of several resent studies that calls the Giant Impact Hypothesis into question.

    Hauri et al., 2011. "High Pre-Eruptive Water Contents Preserved in Lunar Melt Inclusions" [sciencemag.org] 333(6039), 213-215.

  • Mild-mannered high school student, Luna Selene was attending a presentation on radioactivity at New York University when she was bitten by an irradiated moon!
  • ...Sorry but if find this far more convincing [youtube.com] than a bunch of scientists doing what amounts to guessing. Look at the quality...plus it was on tele, twice!
  • Shouldn't the headline say "Findings Cast Doubt On Current Moon Origin theories"?

  • o.O

    Bill O'Reilly was right! We can't explain it!

  • What about a double impact? The first one creates the vast majority of the moon. When the moon eventually cools enough, a second high-velocity impact kicks up Earth material which eventually lands on the moon's surface. Any samples from the moon's surface would be mostly from the second impact. The second impact would kick up more of Earth and less of itself than the first because it would be a high-speed impact.

    My understanding is that a fairly low-speed impact is necessary to kick up sufficient "solid" m

  • I was expecting an Earth-shattering kaboom!

  • how the Moon was formed. It is not the so-called Giant Impact Hypothesis. It is called the Giant Impact Hypothesis and that's what it is an hypothesis, not a theory. It doesn't cast any doubt on the Moon's origins. It is a strike against the GIH. It just means that scientists have to come up with a new idea of how it was formed. Now this isotopic analysis will help to formulate a new hypothesis and even theory about the Moon's origin.

What this country needs is a good five dollar plasma weapon.

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