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My understanding of the theory is that Theia hit the earth, that most of it was absorbed into the earth's surface/ molten core, and that the rest, along with so
by kristianc 15y ago
My understanding of the theory is that Theia hit the earth, that most of it was absorbed into the earth's surface/ molten core, and that the rest, along with some of the earth was ejected out into space.
If that's the case I don't see how there is any way of 'proving' that the isotopic signatures we are matching with those of the moon are 'native' and not already part of some Earth/Theia mix - in which case they'd match with a Moon that was already part of an Earth/Theia mix. Without knowing the composition of the earth 4.5 billion years ago, I'm not sure you can say otherwise?
- jbri 15y agoIf the giant impact theory is correct, Theia must have been about the same size as Mars - roughly a tenth of the mass of the earth. Hence it would have a much larger impact on the makeup of the moon than it would on the makeup of the earth - a difference we would expect to be able to detect if the theory is correct.
- Sharlin 15y agoIt would have a negligible impact on the makeup of the Earth as a whole, but should have a large impact on the composition of Earth's crust (and the mantle, to a lesser extent.) It seems to me that the Theia theory should also predict that Earth's crust and Moon's crust (which are the only parts we can get samples of!) have quite similar composition.