But a potential explanation comes in the form of a rare group of meteorites called enstatite chondrites, which are also nearly identical to Earth. It is true that meteorites from other parts of the solar system bare no isotopic resemblance to either Earth or the Moon. A few years ago, simulations seemed to show that Theia had actually originated in the distant solar system, complicating the hypothesis further. These results are surprising, since no other major bodies in the solar system are that alike, especially in oxygen concentrations. For example, the ratio of oxygen-16 to oxygen-18 is about the same in the Moon as in Earth. One issue with the hypothesis is that samples of lunar rocks reveal that the Moon and Earth have very similar ratios of isotopes - the equivalent of an elemental fingerprint for celestial objects. The Giant Impact Hypothesis is, as your question alludes to, not yet settled. Any iron core that Theia may have had was consumed by Earth’s own core. From this disk, the Moon coalesced thus, models indicate most of Theia’s material ended up as part of the Moon. After slamming into Earth, the outer rocky shells of both Earth and Theia were blasted into a disk of debris around our planet. In the years since, many researchers have modeled what the impact may have looked like. At the time, the Giant Impact Hypothesis had very little to say about what happened to the impactor itself. Davis and I suggested that the Moon was formed when a Mars-sized planetesimal, later called Theia, struck a newly formed Earth about 4.5 billion years ago.
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