Evidence of Protoplanet Found On Moon 105
mrspoonsi (2955715) writes 'Researchers have found evidence of the world that crashed into the Earth billions of years ago to form the Moon. Analysis of lunar rock brought back by Apollo astronauts shows traces of the "planet" called Theia. The researchers claim that their discovery confirms the theory that the Moon was created by just such a cataclysmic collision. The accepted theory since the 1980s is that the Moon arose as a result of a collision between the Earth and Theia 4.5bn years ago. It is the simplest explanation, and fits in well with computer simulations. The main drawback with the theory is that no one had found any evidence of Theia in lunar rock samples. Earlier analyses had shown Moon rock to have originated entirely from the Earth whereas computer simulations had shown that the Moon ought to have been mostly derived from Theia. Now a more refined analysis of Moon rock has found evidence of material thought to have an alien origin.'
Skeptics (Score:5, Interesting)
And the rest of the article discusses the skepticism of this "evidence". To sum it all up, the evidence is the different ratios of oxygen isotopes found between 3 moon rocks and Earth. Most experts are saying the difference in the ratios should be much, much larger, because of how different the ratios of isotopes are in meteorites and other outer solar system bodies. The difference between the earth and moon is so small that other theories are just as likely for explaining it. The counter argument is that maybe all of the inner planets have the same ratios of oxygen isotopes as one another, and it was an inner planet that struck Earth and basically everything involved was made of the same stuff so the differences are small.
I think that until we have actually measured the ratios from Mecury or Venus, we can't assume that every inner planet is exactly the same in that regard, and thus the "evidence" this study has found is actual evidence one way or another. The only thing we know for certain is all the extraterrestrial material we have analyzed so far from the rest of the solar system has had very different ratios of the isotopes, and so this evidence requires a whole new theory about the homogeneousness of the solar system to be true.
Re:Skeptics (Score:5, Interesting)
Re:Skeptics (Score:5, Interesting)
The impact simulations kind of rule that out. I'd say the sample size is a real issue though. Also, there are quite a few assumptions that I'd say are questionable. We've no idea where this protoplanet came from. It could have been from outside the solar system... or it could have been part of earth at one time, jettisoned in a previous impact and came back for revenge. The fact that we have as much information as we do blows my mind. Science is amazing.
Re:Skeptics (Score:4, Interesting)
The only thing we know for certain is all the extraterrestrial material we have analyzed so far from the rest of the solar system has had very different ratios of the isotopes, and so this evidence requires a whole new theory about the homogeneousness of the solar system to be true.
Not exactly. One thing missing from the popular discussions of this question is why we believe that isotope ratios necessarily vary across all larger bodies in the solar system.
It is true that measurements on meteorites show different ratios from what we see on Earth, but no particular conclusion can be drawn from that. It certainly does not follow from "None of the people I measure are the same height" that "No two people anywhere are the same height", so it would be bizarre in the extreme to go from a sample of fairly odd, mostly non-planetary, space rocks to a sweeping generalization about what is necessarily the case across the whole solar system. There may be some theoretical reason for believing this to be the case, but I've never seen it mentioned in any of the articles on this subject.
Furthermore, Theia has a very, very special property: its orbit intersected that of Earth's almost instantly after its formation. This is not the case with meteors, which have been wandering the solar system for more than four billion years, and therefore likely formed in very distant regions. Theia almost by necessity formed in a similar orbit to that of Earth. We know this, because only a body that formed in a similar orbit would likely find itself in a collision with Earth almost immediately after formation.
None of this "proves" or "disproves" anything, mind, because we're talking about knowledge here, not faith. Knowledge is by its nature uncertain, and the quest for certainty is simply an error pursued by pre-scientific peoples (philosophers), no different from the alchemical pursuit of transmutation of base metals into gold, or attempts to build perpetual motion machines, or attempts to trisect angles with nothing but straight-edge and compass.