How did Earth get its water? Moon rocks suggest it might have been here all along.

I note some interesting comments from this reference paper on the subject. Reference paper, The origin of volatile elements in the Earth–Moon system, https://www.pnas.org/content/119/8/e2115726119, 22-Feb-2022.

From the paper, "Although this work challenges the canonical presumption that volatile element depletion of the Moon occurred during the Giant Impact (39⇓–41), it offers considerable advantages on the origin of volatiles in the Earth–Moon system. Based on the most likely scenario anchored by Rb–Sr systematics, the Giant Impact happened comparatively late (after 4.45 Ga), and the Moon formed largely (∼90%) from a strongly volatile-depleted Theia. This is consistent with the gradient of volatile elements observed in solar system materials, it accounts for the difference in the proportion of volatile elements in the Moon and Earth, and it explains the isotopic similarities in the Earth–Moon system. Furthermore, this model is consistent with calculations that suggest the Moon is composed mostly of Theia (15, 16) as well as some independent estimates for the timing of the Giant Impact after ∼4.43 Ga (9, 13). Lastly, the presented scenario suggests that the Earth and Moon formed with roughly the same budget of volatiles present today, and large amounts of such species are not required to be added to the Earth after the Giant Impact."

My note. The giant impact taking place after 4.45 billion years ago or even 4.43 billion years ago, everything is now very crowded. The Faint Young Sun, a Moon with magma ocean (lasted perhaps 200 million years after the giant impact) covering it orbiting very close to Earth, and Earth with Precambrian microorganism fossils dated 4.28 billion years old using zircons and evidence of oceans on Earth along with catastrophic bombardment rates operating during this early period. Plenty to juggle here when explaining the origin of the Earth-Moon system, our abundant water supply, and how life arose during this postulated early period using abiogenesis and how life avoided being destroyed, again, again, and again.
 
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I'm curious how well this isotopic method fits with other models, such as the ones that note the deterium ratio differences across the system, etc.

Also, I suspect the Earth, due to that impact, and perhaps others, seems to be light on water. There is likely more water on the little moon Europa than on Earth. This too may favor the impact story, perhaps.
 

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