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Traces of Theia Found on The Moon

  1. Jun 6, 2014 #1


    Staff: Mentor

    BBC news today have an article Traces of another world found on the Moon

    It says
    Can someone please help me understand. If the sun and our planets formed from the same dust cloud, then why are the isotopic ratios different?
  2. jcsd
  3. Jun 6, 2014 #2
    To quote the NASA website article I cite below “no one knows for sure”. There are some best liked hypotheses, but no strong consensus on which, if any, are most true.

    In short, that the ratio of the 3 stable isotopes of oxygen, 16 (~99.76% on Earth), 17 (0.039%) and 18 (0.201%) (more precisely, the 17O:18O ratio – the 16O:18O ratio varies considerably from sample to sample, for fairly well-understood reasons) is different on Earth than other places it’s been measured (mostly in C chondrite meteorites, more recently on Mars) is an empirical given.

    The Theia, or Giant Impact, hypothesis supposes a planet similar in size and composition to Mars, Theia, struck Earth about 4,500,000,000 years ago, and that the ratio of Theia material : Earth material on the Moon’s surface is higher than on the Earth’s. Validating this by measuring moon rocks (most from the 1969-1972 Apollo missions) bolsters support for the Giant Impact hypothesis. Recent such analysis is described in the linked BBC article.

    Source: ”What Are Isotopes, and Why Should We Care?”, Bob Silberg, NASA Solar System Explorations.
  4. Jun 10, 2014 #3
    Traces, meteorite pieces of: the Moon, Mars, Asteroids, even Venus and stellar grain masses have been found on Earth. That does not mean there was a massive large body collision between the the two resulting in the formation of say the Moon for instance. We found and identified a hand sample mass of stellar grains labelled BCC0001. Although it could have, that does not mean the Earth collided with an entire star.
  5. Jun 10, 2014 #4


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    Science Advisor

    Despite the use of the word "traces" in the BBC headline, the report goes well beyond that, claiming that the moon may be as much as 40 percent Theia.
  6. Jun 10, 2014 #5
    The mechanics just does not work out.

    The scientific community is trying to explain the origin of things planetary they settled with everything forming from collisions....things colliding with one another. In the case of the Pluto's five Moons the Wikipedia editors have gone Walt Disney and have a sentence that says the moons must have the same collision origin because they have the same color, grey. Can you believe that? They also liken its origin to a similarity with the Earth's Moon, which has even gone more Walt Disney than anything previously printed.

    Below is their newest abstract explaining the origin of our Moon: "Identification of the giant impactor Theia in lunar rocks".
    The Moon was probably formed by a catastrophic collision of the proto-Earth with a planetesimal named Theia. Most numerical models of this collision imply a higher portion of Theia in the Moon than in Earth. Because of the isotope heterogeneity among solar system bodies, the isotopic composition of Earth and the Moon should thus be distinct. So far, however, all attempts to identify the isotopic component of Theia in lunar rocks have failed. Our triple oxygen isotope data reveal a 12 ± 3 parts per million difference in ?17O between Earth and the Moon, which supports the giant impact hypothesis of Moon formation. We also show that enstatite chondrites and Earth have different? 17O values, and we speculate on an enstatite chondrite–like composition of Theia. The observed small compositional difference could alternatively be explained by a carbonaceous chondrite–dominated late veneer.

    I'm not sure what is motivating the scientific community forever pushing this theory but they keep pumping new life into this theory from the same angle every 6-9 months.

    Large planetary bodies colliding would result in hundreds if not thousands of smaller bodies of material floating around in irregular shapes. [Asteroids are evidence of that] but you would not expect this collision to form evolving round bodies, which then spring to life forming a terrestrial planet with an adjoining (round) satellite. Because if this were true we would then have to say all planets and their Moons formed the same way.......by destructive collisions. Highly unlikely. While there may be isotopic similarities and geophysical similarities between the Earth and the Moon, the differences are enough at the crystallite/molecular level that there is no way one actually sprang and evolved from the other as the result of a collision.
    What if remnant material was torn away from the Earth in an impact, re-coalesce with its impactor and simply landed on the Moon......just like lunar material lands on Earth from a meteorite impact on the Moon? Have you thought about that Mr. Herwartz?

    Are both Moons around Mars the result of one collision or two collisions? What about Jupiter? Did planets, comets, or asteroids collide with Jupiter forming its Moons, and how many collisions did it take to create its 67 Moons?
  7. Jun 10, 2014 #6
    BBC Meteorites, I suggest before saying too much more, have a look at the wikki: http://en.wikipedia.org/wiki/Moon. When you consider all of the competing theories and all the conditions that such theories would require, the only one which doesn't require special, highly unlikely conditions is the "Great impact". There are many facts about the Earth, Moon and Earth/Moon relationship, which are only supported by the one theory.

  8. Jun 10, 2014 #7
    I think it may be important to note that there are a significant number of kinds of collisions, not just head on impacts of equally solid objects, especially 4+ billion years ago during the Late Heavy Bombardment. Many were molten or only recently and/or partially solidified, as well as made molten either in whole or partially by the energy of the impact, especially at a glancing blow. It is my understanding that extensive super computer time has been spent modeling such collisions and specifically the Earth/Theia question and a significant window of sizes, speeds, temperatures and angles result in similar systems to the Earth/Moon system. There can be many ways in which a body may acquire a satellite(s).
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